Lewis & Short

tŏpĭārĭus, a, um, adj. [topia, II.],

  1. I. of or belonging to ornamental gardening or gardening in gen.: opus, Plin. 15, 30, 39, § 130: herba, i. e. used for borders in gardens, id. 21, 11, 39, § 68; 22, 22, 34, § 76.
  2. II. Substt.
    1. A. tŏpĭārĭus, ii, m., an ornamental gardener, fancy gardener, Cic. Q. Fr. 3, 1, 2, § 5; Plin. 15, 29, 37, § 122; 18, 26, 65, § 242; Plin. Ep. 3, 19, 3; Inscr. Orell. 2966; 4293; cf. Becker, Gallus, 3, p. 27 (2d edit.).
    2. B. tŏpĭārĭa, ae, f. (sc. ars), ornamental or fancy gardening, the topiary art, i. e. that of giving fanciful forms to thickets, trees, etc., of laying out parterres. forming arbors, bowers, etc., Cic. Q. Fr. 3, 1, 2, § 5.
    3. C. tŏpĭārĭum, ii, n. (sc. opus), fancy gardening, topiary-work, Plin. 18, 28, 68, § 265.