NOUN (1)

1. a sharp narrow ridge found in rugged mountains;

The Collaborative International Dictionary of English v.0.48:

Arete \A`r[^e]te"\, n. [F., lit., a sharp fish bone, ridge,
   sharp edge, fr. L. arista beard of grain.] (Geog.)
   An acute and rugged crest of a mountain range or a subsidiary
   ridge between two mountain gorges.
   [Webster 1913 Suppl.]