Definition of "flag"

flag¹

/flæɡ/

noun
countable and uncountable, plural flags
1. A piece of cloth, often decorated with an emblem, used as a visual signal or symbol.
2. An exact representation of a flag (for example: a digital one used in websites).
3. (nautical) A flag flown by a ship to show the presence on board of the admiral; the admiral himself, or his flagship.
4. (nautical, often used attributively) A signal flag.
5. The use of a flag, especially to indicate the start of a race or other event.
6. (computer science) A variable or memory location that stores a true-or-false, yes-or-no value, typically either recording the fact that a certain event has occurred or requesting that a certain optional action take place.
7. (computer science) In a command line interface, a command parameter requesting optional behavior or otherwise modifying the action of the command being invoked.
  Quotations
  This will be used as a help message if the user passes in the --help flag, like so: […]
  2021, Angel Sola Orbaiceta, Hardcore Programming for Mechanical Engineers, pages 19–2
8. (aviation) A mechanical indicator that pops up to draw the pilot's attention to a problem or malfunction.
  Quotations
  I was shooting an IFR approach down the San Francisco slot, when all of a sudden the ILS flag popped up.
  1966, Barry J. Schiff, All about Flying: An Introduction to the World of Flying, page 72
  […] and then the OFF flag popped up and the needle went dead.
  1980, Paul Garrison, Flying VFR in marginal weather, page 139
9. (Britain, uncountable) The game of capture the flag.
10. (geometry) A sequence of faces of a given polytope, one of each dimension up to that of the polytope (formally, though in practice not always explicitly, including the null face and the polytope itself), such that each face in the sequence is part of the next-higher dimension face.
  Quotations
  A flag of P is a sequence (F0, F1, ..., Fm) of faces of P such that dim Fi = i for each i and Fi is a side of Fi+1 for each i < m. […] A regular polytope in X is a polytope P in X whose group of symmetries in <P> acts transitively on its flags.
  1994, John Ratcliffe, Foundations of Hyperbolic Manifolds‎, page 230
  We call P (combinatorially) regular if its automorphism group Γ(P) is transitive on its flags.
  2002, Peter McMullen, Egon Schulte, Abstract Regular Polytopes, Encyclopedia of Mathematics and Its Applications 92, page 31
  Roughly speaking, chiral polytopes have half as many possible automorphisms as have regular polytopes. More technically, the n-polytope P is chiral if it has two orbits of flags under its group Γ(P), with adjacent flags in different orbits.
  2006, Peter McMullen, Egon Schulte, “Regular and Chiral Polytopes in Low Dimensions”, in Harold Scott Macdonald Coxeter, Chandler Davis, Erich W. Ellers, editors, The Coxeter Legacy: Reflections and Projections, page 91
11. (mathematics, linear algebra) A sequence of subspaces of a vector space, beginning with the null space and ending with the vector space itself, such that each member of the sequence (until the last) is a proper subspace of the next.
12. (television) A dark piece of material that can be mounted on a stand to block or shape the light.
  Quotations
  At the other extreme, with limitless budgets all they have to do is dream up amazing lighting rigs to be constructed and operated by the huge team of gaffers and sparks, with their generators, discharge lights, flags, gobos and brutes.
  1999, Des Lyver, Graham Swainson, Basics of Video Lighting, page 103
  Flags and other cutters allow the DP or gaffer to throw large controlled shadows on parts of the scene.
  2012, John Jackman, Lighting for Digital Video and Television, page 86
13. (UK, archaic, slang) An apron.
  Quotations
  Suppose you try a different tack, / And on the square you flash your flag?
  1887, William Ernest Henley, Villon's Straight Tip to All Cross Coves
14. (Internet slang, ACG) A plot or words of a character in an animation, etc., that would usually lead to a specific outcome or event, not logically or causally, but as a pattern of the animation, etc.
verb
third-person singular simple present flags, present participle flagging, simple past and past participle flagged
1. To furnish or deck out with flags.
2. To mark with a flag, especially to indicate the importance of something.
  Quotations
  Walcott was, briefly, awarded a penalty when he was upended in the box but referee Phil Dowd reversed his decision because Bendtner had been flagged offside.
  2011 January 8, Chris Bevan, “Arsenal 1 - 1 Leeds”, in BBC‎
3. (often with down) To signal to, especially to stop a passing vehicle etc.
4. To convey (a message) by means of flag signals.
5. (often with up) To note, mark or point out for attention.
6. (computing) To signal (an event).
7. (computing) To set a program variable to true.
8. To decoy (game) by waving a flag, handkerchief, etc. to arouse the animal's curiosity.
  Quotations
  This method of hunting, however, is not so much practised now as formerly, as the antelope are getting continually shyer and more difficult to flag.
  1885, Theodore Roosevelt, Hunting Trips of a Ranchman
9. (sports) To penalize for an infraction.
10. (chess, intransitive) To lose on time, especially in a blitz game; when using a traditional analog chess clock, a flag would fall when time expired.
11. (chess, transitive) To defeat (an opponent) on time, especially in a blitz game.
12. (firearms) To point the muzzle of a firearm at a person or object one does not intend to fire on.
13. To fail, such as a class or an exam.
14. (biology) In female canids, to signal mating readiness by moving the tail aside to expose the vulva.
  Quotations
  During estrus, most bitches will flirt with males by backing up to them, flagging their tails in the males’ faces, urinating frequently, and generally acting seductive.
  1996, The Complete Book of Dog Breeding, page 9
  She will avert her tail to the side (flagging), standing still when the male mounts.
  2011 January 3, Pete Haswell, “Life and Behaviour of Wolves”, in Wolf Print‎

flag²

/flæɡ/

verb
third-person singular simple present flags, present participle flagging, simple past and past participle flagged
1. (intransitive) To weaken, become feeble.
  Quotations
  He now sees a spirit has been raised against him, and he only watches till it begin to flag.
  1724, Jonathan Swift, “Drapier's Letters”, in 2
  About half way to Wamphray, they met Mitchell's engine. Her speed was flagging badly. Steam was low, and the fire nearly out.
  1950 January, David L. Smith, “A Runaway at Beattock”, in Railway Magazine, page 54
  The sides took it in turns to err and excite before Newcastle flagged and Arsenal signalled their top-four credentials by blowing the visitors away.
  2012 December 29, Paul Doyle, “Arsenal's Theo Walcott hits hat-trick in thrilling victory over Newcastle”, in The Guardian‎
2. To hang loose without stiffness; to bend down, as flexible bodies; to be loose, yielding, limp.
  Quotations
  as loose it [the sail] flagged around the mast
  1817, Thomas Moore, Lalla-Rookh
3. To let droop; to suffer to fall, or let fall, into feebleness.
  Quotations
  The Thousand Loves , that arm thy potent Eye , Must drop their Quivers , flag their Wings
  1709, Mat[thew] Prior, “An Ode”, in Poems on Several Occasions, 2nd edition, London: […] Jacob Tonson […]
4. To enervate; to exhaust the vigour or elasticity of.
  Quotations
  there is nothing that flags the Spirits, disorders the Blood, and enfeebles the whole Body of Man, as intense Studies.
  1670, John Eachard, The Ground and Occasions of the Contempt of the Clergy

flag³

/flæɡ/

noun
plural flags
1. Any of various plants with sword-shaped leaves, especially irises; specifically, Iris pseudacorus.
  Quotations
  [T]he ebbed man, ne'er loved till ne'er worth love,Comes deared by being lacked. This common body,Like to a vagabond flag upon the stream,Goes to and back, lackeying the varying tide,To rot itself with motion.
  c. 1606–1607, William Shakespeare, “The Tragedie of Anthonie and Cleopatra”, in Mr. William Shakespeares Comedies, Histories, & Tragedies […] (First Folio), London: […] Isaac Iaggard, and Ed[ward] Blount, published 1623, [Act I, scene iii]
  Can the rush grow up without mire? can the flag grow without water?
  1611, The Holy Bible, […] (King James Version), London: […] Robert Barker, […], Job 8:11
  And laden barges float / By banks of myosote; / And scented flag and golden flower-de-lys / Delay the loitering boat.
  before 1899, Robert Seymour Bridges, There is a Hill

flag⁴

/flæɡ/

noun
plural flags
1. (obsolete except in dialects) A slice of turf; a sod.
2. A slab of stone; a flagstone, a flat piece of stone used for paving.
3. (geology) Any hard, evenly stratified sandstone, which splits into layers suitable for flagstones.
verb
third-person singular simple present flags, present participle flagging, simple past and past participle flagged
1. (transitive) To pave with flagstones.

flag⁵

/flæɡ/

noun
plural flags
1. A group of feathers on the lower part of the legs of certain hawks, owls, etc.
2. A group of elongated wing feathers in certain hawks.
3. The bushy tail of a dog such as a setter.
4. (music) A hook attached to the stem of a written note that assigns its rhythmic value

Definition of "flag"

flag1

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flag2

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flag3

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flag4

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flag5

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flag¹

flag²

flag³

flag⁴

flag⁵