Lewis & Short

sarrācum (serrā-), i, n.

  1. I. A kind of wagon or cart (acc. to Quint. 8, 3, 21, belonging to vulgar lang.), Sisenn. ap. Non. 195, 29; Cic. Pis. Fragm. ap. Quint. l. l.; Vitr. 10, 1 fin.; Juv. 3, 255; Capitol. M. Aurel. 13; Amm. 31, 2, 18.
  2. II. Transf., the Wain, a constellation: frigida Bootae, Juv. 5, 23.