Lewis & Short

būcŭlus (also bōcŭlus), i, m. dim. [bos],

  1. I. a young bullock, a steer, Col. 6, 2, 4; Front. Strat. 1, 5, 26.
    More freq. and class.,
  2. II. Subst.: būcŭla, ae, f., a young cow, a heifer, Verg. G. 1, 375; 4, 11; id. E. 8, 86.
    1. B. As a work of art, Cic. Div. 1, 24, 48. The statue of a brazen cow at Athens, the work of Myron, was especially distinguished, Cic. Verr. 2, 4, 60, § 135; id. Div. 1, 24, 48; cf. Plin. 34, 8, 19, § 57.