Lewis & Short

văcerra, ae, f., a log, stock, post.

  1. I. Lit., Col. 9, 1, 3; 9, 1, 9; 6, 19, 2.
  2. II. Transf., like stipes, and our stock, block, as a term of abuse applied to a stupid person: vecorde et malefica vacerra, Liy. Andron. ap. Fest. p. 375 Müll. (Com. Fragm. v. 7 Rib.).