(biochemistry) A specially altered nucleotide end to the 5′ end of precursor messenger RNA and some other primary RNA transcripts as found in eukaryotes and caliciviruses, vital to creating mature messenger RNA which is then able to undergo translation.

(Britain) Ellipsis of if the cap fits, wear it.

(humorous) A metaphorical piece of headgear supposedly worn by a person to assist them in thinking about how to solve a problem.

A celebrated granite dome in Yosemite National Park. / An unusual hot spring in Yellowstone National Park. / A prominent peak on Mount Rainier.

A brimless felt cap, such as the Phrygian cap or pileus, emblematic of a slave's manumission in the ancient world. / A magic mushroom, Psilocybe semilanceata.

A city on the north coast of Haiti.

(construction) A sheet, often granule-surfaced, used as the top ply of some roof membranes and/or flashings.

The cap that closes the opening of a tank, e.g. the fuel tank of a car, through which the tank can be filled.

(now historical) A protective cap on the end of a gunstock. / (aeronautics) The protective covering on the end of an aircraft fuselage.

A type of bottle cap made by pressing a circular piece of metal around the top of the bottle.