(noun; Latin os
, mouth; facere
, to make): 1. An opening into a cavity
; a mouth-like opening.
2. (Arthropoda: Crustacea) In sessile Cirripedia, the opening in the wall occupied by the operculum
See also: aperture. 3. (Bryozoa) The opening on the margin of the orificial wall through which the lophophore passes.