Definition of "define"

define

/dɪˈfaɪn/

verb
third-person singular simple present defines, present participle defining, simple past and past participle defined
1. To determine with precision; to mark out with distinctness; to ascertain or exhibit clearly.
  Quotations
  Rings […] very distinct and well defined.
  1704, I[saac] N[ewton], “(please specify |book=1 to 3)”, in Opticks: Or, A Treatise of the Reflexions, Refractions, Inflexions and Colours of Light. […], London: […] Sam[uel] Smith, and Benj[amin] Walford, printers to the Royal Society, […]
  Turbines have been around for a long time—windmills and water wheels are early examples. The name comes from the Latin turbo, meaning vortex, and thus the defining property of a turbine is that a fluid or gas turns the blades of a rotor, which is attached to a shaft that can perform useful work.
  2013 July-August, Lee S. Langston, “The Adaptable Gas Turbine”, in (Please provide the book title or journal name)
2. (obsolete) To settle, decide (an argument etc.)
  Quotations
  These warlike Champions, all in armour shine, / Assembled were in field the chalenge to define.
  1596, Edmund Spenser, “Book IV, Canto III”, in The Faerie Queene. […], London: […] [John Wolfe] for William Ponsonbie
3. To express the essential nature of something.
  Quotations
  Cantor defined a one-to-one correspondence between the points of the square and the points of the line segment. Every point in the square was associated with a single point in the segment; every point in the segment was matched with a unique point in the square.
  2013 May-June, Brian Hayes, “Crinkly Curves”, in American Scientist, volume 101, number 3, page 178
4. To state the meaning of a word, phrase, sign, or symbol.
5. To describe, explain, or make definite and clear; used to request the listener or other person to elaborate or explain more clearly his or her intended meaning of a word or expression.
6. To demark sharply the outlines or limits of an area or concept.
  Quotations
  Few concepts are as emotionally charged as that of race. The word conjures up a mixture of associations—culture, ethnicity, genetics, subjugation, exclusion and persecution. But is the tragic history of efforts to define groups of people by race really a matter of the misuse of science, the abuse of a valid biological concept?
  2012 March-April, Jan Sapp, “Race Finished”, in American Scientist, volume 100, number 2, page 164
7. (mathematics) To establish the referent of a term or notation.
noun
plural defines
1. (programming) A kind of macro in source code that replaces one text string with another wherever it occurs.
  Quotations
  From the computer programming perspective, Java looks like C and C++ while discarding the overwhelming complexities of those languages, such as typedefs, defines, preprocessor, unions, pointers, and multiple inheritance.
  1996, James Gosling, Henry McGilton, The Java Language Environment
  Anyone who has attempted to do OO programming in a conventional language using defines will find out that it is impossible to realize the benefits easily, if at all, without compiler support.
  1999, Ian Joyner, Objects unencapsulated: Java, Eiffel, and C++, page 309