ramus Syllabification: (ra·mus)Pronunciation: /ˈrāməs/Definition of ramus noun (plural rami /-ˌmī/) 1 Anatomy an arm or branch of a bone, in particular those of the ischium and pubes or of the jawbone. a major branch of a nerve. 2 Zoology a structure in an invertebrate that has the form of a projecting arm, typically one of two or more that are conjoined or adjacent. a barb of a feather. Origin: mid 17th century: from Latin, literally 'branch'ramus in other Oxford dictionaries Definition of ramus in the British & World English dictionary