A hole or apertupe in a door or lock, for receiving a key.
2.
(a)
(Carp.) A hole or excavation in beams intended to be joined together, to receive the key which fastens them.
(b)
(Mach.) A mortise for a key or cotter.
Keyhole limpet (Zool.), a marine gastropod of the genus Fissurella and allied genera. See Fissurella.
Keyhole saw, a narrow, slender saw, used in cutting keyholes, etc., as in doors; a kind of compass saw or fret saw.
Keyhole urchin (Zool.), any one of numerous clypeastroid sea urchins, of the genera Melitta, Rotula, and Encope; so called because they have one or more perforations resembling keyholes.
