اوسآسٌ [The myrtle;] a certain kind of tree, (S, Msb, K,) well known, (S, K,) fragrant, (IDrd, M, Msb,) and evergreen, abundant in the land of the Arabs, growing in the plains and mountains, and increasing so as to become a great tree: (AHn, M, TA:) n. un. with ة: (AHn, M, Msb, K:) IDrd says, I think it an adventitious word, although used by the Arabs, and occurring in chaste poetry. (M, TA.)