Keyhole /(?)/

Key·hole

Keyhole

n.
  1. A hole or apertupe in a door or lock, for receiving a key.
  2. A hole or excavation in beams intended to be joined together, to receive the key which fastens them. (Carp.)

Phrases & Compounds
Keyhole limpet
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
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.