'Keyhole urchin' definitions:

Definition of 'Keyhole urchin'

From: GCIDE
  • Keyhole \Key"hole`\, n.
  • 1. A hole or apertupe in a door or lock, for receiving a key. [1913 Webster]
  • 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. [1913 Webster]
  • 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. [1913 Webster]