Oxford Advanced American Dictionary

Definition of hat noun from the Oxford Advanced Learner's Dictionary

Oxford3000

hat

noun
hat pronunciation English hæt hat pronunciation American hæt
 
1 a covering made to fit the head, often with a brim, (= a flat edge that sticks out) and worn out of doorsa straw/woolly, etc. hatto put on/take off a hat2 (informal) a position or role, especially an official or professional role, when you have more than one such roleI'm wearing two hats tonight—parent and teacher.I'm telling you this with my lawyer's hat on, you understand. see also old hat
Idioms

go hat in hand (to somebody)

(North American English) (British English go cap in hand (to somebody)) to ask somebody for something, especially money, in a very polite way that makes you seem less important

keep something under your hat

(informal) to keep something secret and not tell anyone else

my hat

(old-fashioned, British English) used to express surprise

out of a/the hat

if something such as a name is picked out of a/the hat, it is picked at random from a container into which all the names are put, so that each name has an equal chance of being picked, in a competition, etc.

I take my hat off to somebody

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hats off to somebody

(both especially British English) (North American English usually I tip my hat to somebody) (informal) used to say that you admire somebody very much for something they have done

throw your hat into the ring

to announce officially that you are going to compete in an election, a competition, etc.
more at at the drop of a hat at drop noun, I'll eat my hat at eat, knock somebody/something into a cocked hat at knock verb, pass the hat round/around at pass verb, pull something/a rabbit out of the hat at pull verb, talk through your hat at talk verb