(noun; Latin aperire
, to open): 1. An opening or hole, cleft
, or gap
2. (Arthropoda: Crustacea) The postero-ventral opening into the mantle cavity of barnacles
See also: orifice. 3. (Bryozoa: Stenolaemata) The terminal skeletal opening of a zooid. 4. (Mollusca) An opening at the last-formed margin of a shell, providing the outlet for the head-foot mass.