[count] 1 a : a small, soft hat that often has a hard curved part (called a visor) that extends out over your eyes
▪ a Harvard University cap [=a cap that has the name or symbol of Harvard University on it] ▪ a knit/knitted cap ▪ his wool/tweed cap — see also baseball cap
b : a covering for a person's head that is worn for a special purpose
▪ a shower/bathing cap [=a head covering that people wear to keep their hair dry when they are showering/swimming] — see also thinking cap
c : a hat that people with particular jobs wear while working
▪ a painter's cap ▪ a surgeon's cap, gown, and gloves 2 : a part or object that covers the end or top of something
▪ a bottle cap ▪ a lens cap ▪ a pill bottle with a childproof cap ▪ Put the cap back on the marker when you are done using it. 3 : a part that forms the top of something
▪ a bird with a black cap [=a black section of feathers on the top of its head] ▪ a mushroom cap [=the top part of a mushroom] 4 : a limit on the amount of money that can be spent, given, charged, etc., for something
▪ a spending cap ▪ a cap on political donations ▪ a cap on doctor's fees 5 : a paper or metal container that holds an explosive substance
▪ a blasting cap 6 informal : a capital letter — usually plural ▪ e-mails written in all caps ▪ She signed the letter with her name in caps: KIM. 7 : a hard substance that is shaped to look like a healthy tooth and used to cover a damaged tooth 8 Brit, sports a : an opportunity to play for your school or country
▪ He won his first cap against Columbia when he was 22.
b : a player chosen to play for a country's team 9 Brit : diaphragm 3