Abactores, Abigeatores, or Abigei are terms used to signify those guilty of cattle-stealing (abigeatus), which the Roman practice distinguished from ordinary furtum (q.v.), when the theft was of a sufficiently serious kind. The stealing of a single horse or ox was abigeatus, but to steal less than ten sheep or four pigs was only furtum. It was an aggravation of the offence to steal the animals from a pen or other enclosure, or for the abactor to carry weapons. The punishment was at the discretion of the magistrate, and ranged from banishment and degradation from rank to penal servitude and death. Cf. Dig. 47 14.

Harper's Dictionary of Classical Literature, ed. Harry Thurston Peck, MA, PHD (NY: American Book Co. 1923) p 1-2.