1.  fossa(n = noun.shape) pit - a concavity in a surface (especially an anatomical depression);

2.  fossa(n = noun.animal) genus fossa - monotypic genus of Madagascar civets closely related to palm civets;

3.  fossa(n = noun.animal) cryptoprocta ferox, fossa cat - largest carnivore of Madagascar; intermediate in some respects between cats and civets;

   A pit, groove, cavity, or depression, of greater or less depth; as, the temporal fossa on the side of the skull; the nasal fossæ containing the nostrils in most birds. [1913 Webster]

fossa, n. (pl. fossae) Anat. a shallow depression or cavity.

Etymology:
L, = ditch, fem. past part. of fodere dig