(idiomatic) To do something surprising and beneficial that is unexpected.

(New England, idiomatic, obsolete) To be drunk.

A stereotypically Scottish novelty hat: a tartan tam-o'-shanter with false ginger hair attached.

Alternative form of hand someone his hat

(chiefly US, idiomatic) To require someone to depart; to dismiss someone.

(idiomatic, usually humorous) Prepare for a shock! / Used other than figuratively or idiomatically: see hold, onto, hat.

plural of white top-hat transform

(mathematics, signal processing) A form of the top-hat transform that finds the elements in the input image that are darker than their surroundings.

plural of black top-hat transform

(mathematics, signal processing) A form of the top-hat transform that finds the elements in the input image that are brighter than their surroundings.