or FOSSE, in Fortification, &c. a ditch or moat. The word is French, formed of the Latin par- ticle fossum, of the verb fodio, "I dig."

Foss, Fossa, in Anatomy, a kind of cavity in a bone, with a large aperture, but no exit or perforation. When the aperture is very narrow, it is called a sinus.

Foss is particularly used for the cavity or denture in the back part of the neck.

FOSSA MAGNA, or NAVICULARIS, is an oblong ca- vity, forming the inside of the pudendum muliebre, and which presents itself upon opening the labia; and in the middle whereof are the carunculae myrtiformes. See ANATOMY.