Lewis & Short

glossa, ae, f., = γλῶσσα, an obsolete or foreign word that requires explanation; for the usual glossema, Aus. Ep. 127 (in Quint. 1, 1, 35, written as Greek).
Hence, glossae, a term applied to collections of such words with explanations: tesca aiunt sancta esse, Qui glossas scripserunt, Varr. L. L. 7, § 10 Müll; cf. glossema.