βοῦς
I. Lat. bos (bov-is), a bullock, bull, ox, or a "cow", in pl. "oxen or kine, cattle", Hom., etc.
II. = βοείη or βοέη (always fem.), "an ox-hide shield", Il.
III. proverb., βοῦς ἐπὶ γλώσσηι βέβηκε, βοῦς ἐπὶ γλώσσης ἐπιβαίνει, of people who keep silence from some weighty reason, from the notion of a heavy body keeping down the tongue, Theogn., Aesch.