Definition of "passerine" in English

adjective

Of or relating to the Passeriformes order of perching birds, which are generally anisodactyl (“having three toes pointing forward and one back, which facilitates perching”).
(archaic) Chiefly in the former names of some birds: approximately the size of a sparrow.

noun

Any bird of the order Passeriformes, which comprises more than half of all bird species.