Definition of "tweak"

tweak

/twiːk/

verb
third-person singular simple present tweaks, present participle tweaking, simple past and past participle tweaked
1. (transitive) To pinch and pull with a sudden jerk and twist; to twitch.
2. (transitive, informal) To adjust slightly; to fine-tune.
  Quotations
  Economics is a messy discipline: too fluid to be a science, too rigorous to be an art. Perhaps it is fitting that economists’ most-used metric, gross domestic product (GDP), is a tangle too. […] But as a foundation for analysis it is highly subjective: it rests on difficult decisions about what counts as a territory, what counts as output and how to value it. Indeed, economists are still tweaking it.
  2013 August 3, “Boundary problems”, in The Economist, volume 408, number 8847
  Yet on January 10th, only weeks before the charter was due to come into force, the prime minister said his government was tweaking the draft.
  2017 January 14, “Thailand's new king rejects the army's proposed constitution”, in The Economist‎
3. (transitive) To tease, to annoy; to get under the skin of (someone, typically so as to irritate them, or by extension to enamor, frighten, etc).
  Quotations
  Oh, he loved to tweak people and say things like "Hiya sweetums" to me because that was not exactly de rigueur in front of a bunch of strong feminists. He had this enormous sense of humor. I never knew what he was going to say.
  1995, Alida Brill, Feminist Press, A Rising Public Voice: Women in Politics Worldwide, Feminist Press at CUNY , page 177
  I know what kinds of intervals and melodies tweak people—I know how to make people's skin crawl, how to make them shiver. I can't say it works on all listeners. There are some people, such as overly trained composers and theorists ...
  2003, Ann McCutchan, The Muse that Sings: Composers Speak about the Creative Process, Oxford University Press on Demand, page 92
  “Russia needs leadership and he knows how to tweak people.” He grinned, “He made a convert of me,” chuckling. “I wanted to lead him by the hand, now I follow him like a puppy dog.”
  2006, Clarence Rockey, Carlisle Trace President of the People, Lulu.com, page 171
  But I know he likes to tweak people. For a while he was giving Colette, the receptionist, a hard time, until she learned to ignore him. But that ability that lets him see how to tweak people makes him a superb salesman.
  2011, Sara J. Henry, Learning to Swim: A Novel, Crown, page 183
4. (intransitive, US, slang) To abuse methamphetamines, especially crystal meth.
5. (intransitive, US, slang) To exhibit extreme nervousness, evasiveness when confronted by authorities, compulsiveness, erratic motion, excitability, etc, due to or mimicking the symptoms of methamphetamine abuse.
noun
plural tweaks
1. A sharp pinch or jerk; a twist or twitch.
2. A slight adjustment or modification.
3. Trouble; distress; tweag.
4. (obsolete, slang) A prostitute.
  Quotations
  Thence to Bautree, as I came there, From the bushes near the lane, there Rush'd a tweak in gesture flanting With a leering eye, and wanton: But my flesh I did subdue it Fearing lest my purse should rue it.
  1638, Richard Brathwait, edited by Thomas Gent, Barnabae Itinerarium; or Drunken Barnaby's four journeys to the north of England: In Latin and English metre‎, published 1852, page 113
5. (cryptography) An additional input to a block cipher, used in conjunction with the key to select the permutation computed by the cipher.