What is Aratrum Terrae?

Legal Definition
The term aratrum terræ, in ancient law books, meant as much land as can be tilled with one plough—Hoc manerium est 30 aratrorum.

Aratura terræ was an ancient service which the tenant was to do his lord, by ploughing his land.
-- Wikipedia
Legal Definition
In old English law. A plow of land; a plow-land; as much land as could be tilled with one plow. Whis-haw.
-- Black's Law Dictionary
Legal Definition
Land ploughable with one plough.
-- Ballentine's Law Dictionary