flag

noun

1. (countable)A piece of cloth, often decorated with an emblem, used as a visual signal or symbol.

   “The vote in the Bundestag (parliament) on Thursday makes defiling foreign flags equal to the crime of defiling the German flag. […] The new law also applies to acts of defilement besides burning, such as publicly ripping a flag up.”

2. (countable, uncountable)The design that could be placed on a flag, typically a rectangular graphic that is used to represent an entity (like a country, organisation or group of people) or an idea.

   “The flag of France has three vertical stripes.”

3. (countable, uncountable)A flag flown by a ship to show the presence on board of the admiral; the admiral himself, or his flagship.
4. (attributive, countable, often, uncountable)A signal flag.
5. (countable, uncountable)The use of a flag, especially to indicate the start of a race or other event.
6. (countable, uncountable)A variable or memory location that stores a Boolean 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. (countable, uncountable)In a command line interface, a command parameter requesting optional behavior or otherwise modifying the action of the command being invoked.

   “This will be used as a help message if the user passes in the --help flag, like so: […]”

8. (countable, uncountable)A mechanical indicator that pops up to draw the pilot's attention to a problem or malfunction.

   “I was shooting an IFR approach down the San Francisco slot, when all of a sudden the ILS flag popped up.”

   “[…] and then the OFF flag popped up and the needle went dead.”

9. (British, uncountable)The game of capture the flag.
10. (countable, uncountable)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.

    “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.”

    “We call P (combinatorially) regular if its automorphism group Γ(P) is transitive on its flags.”

    “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.”

11. (countable, uncountable)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. (countable, uncountable)A dark piece of material that can be mounted on a stand to block or shape the light.

    “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.”

    “Flags and other cutters allow the DP or gaffer to throw large controlled shadows on parts of the scene.”

13. (UK, archaic, countable, slang, uncountable)An apron.

    “Suppose you try a different tack, / And on the square you flash your flag?”

14. (Internet, countable, uncountable)An indication that a certain outcome or event is going to happen, deduced not logically or causally, but as a pattern in a piece of media. Chiefly used in video games and adjacent media, especially visual novels, it is typically described as being raised or set by the plot or words of a character.

    “set a death flag”

    “raise the heroine's flags (in a galge)”

15. (UK, countable, obsolete, slang, uncountable)A groat; fourpence.

    “[…] the orator pulled out a tremendous black doll, bought for a ‘flag’ (fourpence) of a retired rag-merchant, and dressed up in Oriental style.”

16. Any of various plants with sword-shaped leaves, especially irises; specifically, Iris pseudacorus.

    “[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.”

    “Can the rush grow up without mire? can the flag grow without water?”

    “And laden barges float By banks of myosote; And scented flag and golden flower-de-lys Delay the loitering boat.”

17. A slice of turf; a sod.
18. A slab of stone; a flagstone, a flat piece of stone used for paving.

    ““Huliganï,” fumed Pnin, shaking his head—and slipped slightly on a flag of the path that meandered down a turfy slope among the leafless elms.”

    “On market days the farmers would come in before going home - Tysons and Lindsays and Birketts and Longmires and Boows and Dawsons - and their dogs would lie in heaps on the flags while they themselves supped Gerald's ale.”

19. Any hard, evenly stratified sandstone, which splits into layers suitable for flagstones.
20. A group of feathers on the lower part of the legs of certain hawks, owls, etc.
21. A group of elongated wing feathers in certain hawks.
22. The bushy tail of a dog such as a setter.
23. A hook attached to the stem of a written note that assigns its rhythmic value

verb

1. To furnish or deck out with flags.
2. To mark with a flag, especially to indicate the importance of something.

   “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.”

3. (often, with-down)To signal to, especially to stop a passing vehicle etc.

   “Please flag down a taxi for me.”

   “The electric locomotive is accompanied by a shunter who, in addition to his normal duties, flags the trains over the unprotected level crossings and opens the gates through which the line passes.”

4. To convey (a message) by means of flag signals.

   “to flag an order to troops or vessels at a distance”

5. (often, with-up)To note, mark or point out for attention.

   “I've flagged up the need for further investigation into this.”

   “Users of the Internet forum can flag others' posts as inappropriate.”

6. To signal (an event).

   “The compiler flagged three errors.”

7. To set a program variable to true.

   “Flag the debug option before running the program.”

8. To decoy (game) by waving a flag, handkerchief, etc. to arouse the animal's curiosity.

   “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.”

9. To penalize for an infraction.

   “The defender was flagged for unsportsmanlike conduct.”

10. (intransitive)To lose on time, especially in a blitz game; when using a traditional analog chess clock, a flag would fall when time expired.

    “Mark Dvoretsky (2014), For Friends & Colleagues, volume 1, →ISBN: “Indeed, I usually spent an hour to an hour and a half on my game, never found myself in time pressure, never once flagged in my entire life, except in blitz games, of course.””

11. (transitive)To defeat (an opponent) on time, especially in a blitz game.

    “White was winning positionally, but Black managed to flag him and win.”

12. 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.

    “After he flagged Algebra, Mike was ineligible for the football team.”

14. In female canids, to signal mating readiness by moving the tail aside to expose the vulva.

    “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.”

    “She will avert her tail to the side (flagging), standing still when the male mounts.”

15. (intransitive)To weaken, become feeble.

    “His strength flagged toward the end of the race.”

    “He now sees a spirit has been raised against him, and he only watches till it begin to flag.”

    “About half way to Wamphray, they met Mitchell's engine. Her speed was flagging badly. Steam was low, and the fire nearly out.”

    “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.”

16. To hang loose without stiffness; to bend down, as flexible bodies; to be loose, yielding, limp.

    “as loose it [the sail] flagged around the mast”

17. To let droop; to suffer to fall, or let fall, into feebleness.

    “The Thousand Loves , that arm thy potent Eye , Must drop their Quivers , flag their Wings”

18. To enervate; to exhaust the vigour or elasticity of.

    “there is nothing that flags the Spirits, disorders the Blood, and enfeebles the whole Body of Man, as intense Studies.”

19. (transitive)To pave with flagstones.

    “Fred is planning to flag his patio this weekend.”