Lewis & Short

dĕcĭmānus or dĕcŭmānus (v. decimus), a, um, adj. [decimus], of or belonging to the tenth part.

  1. I. Prop.
    1. A. Of tithes, as a tax: ager, that pays tithes, Cic. Verr. 2, 3, 6; cf.: frumentum, i. e. a tithe of the produce, id. ib. 2, 3, 5 fin. and 81: oleum, Lucil. ap. Non. 445, 19.
      1. 2. Subst.: dĕcŭmānus, i, m., a farmer of tithes, tithe-gatherer, Cic. Verr. 2, 2, 13; 71; 2, 3, 8 et saep.: (perh. sarcastically) dĕcŭmāna, ae, f., the wife of a tithefarmer, Cic. Verr. 2, 3, 33; for which decumana mulier, id. ib. 34.
    2. B. Of the tenth cohort: miles, Auct. B. Afr. 16, 2; and oftener absol. dĕcŭmāni, ōrum, m., id. ib. § 1; Auct. B. Hisp. 30 fin.; Tac. H. 5, 20; Suet. Caes. 70.
      Esp.: porta decumana, the main entrance of a Roman camp, placed the farthest from the enemy (because the tenth cohort of each legion was there encamped), opposite the porta praetoria, Caes. B. G. 2, 24; 3, 25 fin.; 6, 37; id. B. C. 3, 69; Liv. 3, 5; 10, 32 fin. al.; cf. Veg. Mil. 1, 23; Smith’s Ant. p. 222, a.
    3. C. Decumanus limes, in agriculture, a boundary line drawn from east to west, opp. cardo (v. h. v.), Col. 12, 43, 2; Plin. 17, 22, 35, § 169; 18, 34, 77, § 337; cf. Paul. ex Fest. p. 71, 14; v. Wordswörth, Fragm. p. 446.
  2. II. Meton., considerable, large, immense (cf.: decimus, decem, decies, etc.): accipensere, Lucil. ap. Cic. Fin. 2, 8, 24: DECUMANA ova’ dicuntur et DECUMANI fluctus, quia sunt magna, Paul. ex Fest. p. 71, 5; cf. ib. 4, 7 Müll.