Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
† būcĕrus (būcĕrĭus, Lucr. 2, 663), a, um, adj., = βούκερως, having the horns of a bullock, ox-horned (perh. only in the foll. exs.): bucerum pecus de bubus dicimus, Paul. ex Fest. p. 32 Müll.: bucera saecla, the race of horned caltle, Lucr. 5, 864; so id. 6, 1236; imitated by Ovid: armenta, * Ov. M. 6, 395: buceriae greges, Lucr. 2, 663 (quoted by Non. p. 80, 27, and p. 208, 21).