Lewis & Short

1. arbuscŭla, ae, f. dim. [from arbor, as majusculus, minusculus, from major, minor].

  1. I. A small tree, shrub.
    1. A. Lit., Varr. R. R. 3, 15; Col. 5, 10, 7; 5, 11, 13; 11, 2, 79.
    2. B. Transf., of a tuft of feathers: arbuscula crinita, i. e. the crown on the head of the peacock, Plin. 11, 37, 44, § 121.
  2. II. In mechanics, a movable machine for propelling military engines, Gr. ἁμαξόποδες, Vitr. 10, 20.