The Collaborative International Dictionary of English v.0.48:
Ramus \Ra"mus\ (r[=a]"m[u^]s), n.; pl. Rami (r[=a]"m[imac]). (Nat. Hist.) A branch; a projecting part or prominent process; a ramification. [1913 Webster]WordNet (r) 3.0 (2006):
ramus n 1: the posterior part of the mandible that is more or less vertical