A warning of an imminent explosion in a confined space, especially a grenade or blasting charge. / (slang) A generalized warning that something is about to happen.

A small hole through which the propellant charge of a cannon or muzzleloading gun is ignited.

(poker, chiefly in the plural) A playing card, dealt face down, that the holder need not reveal until the showdown / (by extension) Something held in reserve, or concealed, until it is useful

(UK) A secret compartment in a large house, used as a hiding place for priests during the times when Catholicism was forbidden.

The hand-hole, or manhole, in a steam boiler, by means of which sediment can be removed.

(military slang) A concealed place where one can hide in safety, especially during a war; a dugout.

(slang) The state of dissociation from (and lack of control over) the body commonly experienced after taking relatively high doses of the drug ketamine.

(physics) A vacant position in the atomic lattice of a conductor where an electron would normally be present

(chiefly Australia, New Zealand) An area for swimming in a stream or river.

(music) A sound hole, shaped like the letter s, through the top surface of a string instrument.