Definition
A cattle thief; specifically, one who steals livestock by driving animals away from a herd in numbers, rather than taking a single animal. The term originates in Roman law and describes a particular scale and method of theft — the systematic abstraction of cattle or other animals from a herd with intent to steal them. Also called abigeus.
Common Language
Modern common usage (Wiktionary): One who steals and drives away cattle or beasts by herds or droves; a cattle rustler.
Historical common usage (Webster's 1913): One who steals and drives away cattle or beasts by herds or droves. [Obs.]
The common and legal meanings are closely aligned, but the legal term carries a specific Roman law context that the common definitions do not convey. In Roman law, the distinction between an abactor and an ordinary thief (fur) was not merely descriptive — taking animals in numbers from a herd was treated as a graver offense than the isolated theft of a single beast, reflecting the economic and social severity of large-scale livestock depredation.
Why It Matters in Research
Abactor is a term of purely historical and Roman law significance. Researchers will encounter it almost exclusively in two contexts: treatises on Roman or civil law, and older common law dictionaries that imported Roman terminology into English legal vocabulary. It has no operative role in modern Anglo-American criminal law, where livestock theft is handled under general larceny or specific livestock theft statutes.
The chief research trap is treating abactor and abigeus as strict synonyms requiring distinction. The historical sources use them interchangeably, with abigeus being the more common form. A researcher who encounters one should search for both when working through older civil law materials.
Burrill's citation to Gibbon's Decline and Fall of the Roman Empire is a useful signal: by the time English legal lexicographers were defining this term, they were drawing on historical and literary sources rather than living legal practice. This places abactor firmly in the antiquarian layer of Anglo-American legal dictionaries — terms preserved for completeness and civil law context, not for practical application.
Historical Dictionary Support
The three source dictionaries are in full agreement on substance. Black's (1st ed.) and Black's (2nd ed.) both trace the term to Roman law and flag abigeus as the more common alternative. Burrill adds useful texture: the Latin root abigere (to drive away) anchors the meaning, and Burrill's reference to Gibbon confirms that even in the nineteenth century, this term was being sourced from Roman historical records rather than contemporary legal practice.
None of the historical dictionaries attempt to apply the term to English common law livestock theft, which is itself informative. English law developed its own vocabulary for cattle stealing, and abactor never migrated into operative use in English courts. Blount and Cowell — both cited by Black's and Burrill — are seventeenth-century English legal antiquarians who preserved the term as a matter of scholarly completeness, not practical guidance.
What the historical sources do not address is any formal threshold distinguishing abactor-scale theft from ordinary theft in Roman law. Burrill gestures at this with the phrase "smaller animals in numbers," but none of the dictionaries quantify the distinction. Researchers requiring precision on the Roman law elements should look beyond legal dictionaries to civil law scholarship.