The Collaborative International Dictionary of English v.0.48:

Shrub \Shrub\, n. [Ar. shirb, shurb, a drink, beverage, fr.
   shariba to drink. Cf. Sirup, Sherbet.]
   A liquor composed of vegetable acid, especially lemon juice,
   and sugar, with spirit to preserve it.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Shrub \Shrub\, n. [OE. schrob, AS. scrob, scrobb; akin to Norw.
   skrubba the dwarf cornel tree.] (Bot.)
   A woody plant of less size than a tree, and usually with
   several stems from the same root.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Shrub \Shrub\, v. t.
   To lop; to prune. [Obs.] --Anderson (1573).
   [1913 Webster]

WordNet (r) 3.0 (2006):

shrub
    n 1: a low woody perennial plant usually having several major
         stems [syn: shrub, bush]