Lewis & Short

complŭvĭum, ii, n. [compluit, I.],

  1. I. a quadranguiar open space in the middle of a Roman house, which collected the rain-water flowing from the roofs and conducted it to a basin (impluvium) placed below, Varr. L. L. 5, § 161 Müll.; Paul. ex Fest. p. 108, 14 ib.; Varr. R. R. 1, 13, 3; Vitr. 6, 3, 1; * Suet. Aug. 92; cf. impluvium, II. A.
    Hence,
  2. II. Meton., a quadrangular support for vines, Col. 4, 24, 14 Schneid. N. cr.; 4, 26, 3; cf. compluviatus.