Key"hole` (?), n.
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.
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.
© Webster 1913.