hat / hat/ • n. a shaped covering for the head worn for warmth, as a fashion item, or as part of a uniform. ∎  used to refer to a particular role or occupation of someone who has more than one: wearing her scientific hat, she is director of a pharmacology research group.PHRASES: hat in hand used to indicate an attitude of humility: standing on the stoop of his ex-wife's house, hat in hand.keep something under one's hat keep something a secret.pass the hat collect contributions of money from a number of people for a specific purpose.pick something out of a hat select something, esp. the winner of a contest, at random.take one's hat off to (or hats off to) used to state one's admiration for (someone who has done something praiseworthy): I take my hat off to anyone who makes it work hats off to emergency services for prompt work in the wake of the storms.talk through one's hatsee talk.throw one's hat in (or into) the ring express willingness to take up a challenge, esp. to enter a political race.DERIVATIVES: hat·ful / -ˌfoŏl/ n. (pl. -fuls.) hat·less adj.hat·ted adj. [in comb.] a white-hatted cowboy.

hat be all hat and no cattle informal US expression meaning, tend to talk boastfully without acting on one's words.
black hat (or white hat) used in reference to the bad (or good) party in a situation (from the colour of hat traditionally worn by the bad (or good) character in Western films).
hat-trick three successes of the same kind, especially consecutive ones within a limited period, originally referring in cricket to the club presentation of a new hat (or some equivalent) to a bowler taking three wickets successively.
keep something under one's hat keep something a secret.
pass the hat round collect contributions of money from a number of people for a specific purpose.
throw one's hat into the ring express willingness to take up a challenge.

hat OE. hætt, corr. to ON. hǫttr hood, cowl :- Gmc. *χattuz; rel. to HOOD.
Hence hatter XIV.

HAT housing action (or association) trust