Lewis & Short

fosso, āvi, ātum, 1, v. freq. a. [fodio], to dig, pierce (ante-and post-class.): corpora telis, Enn. ap. Varr. L. L. 7, § 100 (Ann. v. 569 ed. Vahl.).
Hence,

    1. 1. fossātum, i, n., a ditch, fosse, Pall. Sept. 13; Capitol. Gord. 28; Veg. Mil. 4, 16.
    2. 2. fossātus, i, m., a boundary, Auct. Rei Agr. p. 254 and 267 Goes.