The Collaborative International Dictionary of English v.0.48:

Tuberous \Tu"ber*ous\, a. [L. tuberosus: cf. F. tub['e]reux. See
   Tuber, and cf. also Tuberose.]
   [1913 Webster]
   1. Covered with knobby or wartlike prominences; knobbed.
      [1913 Webster]

   2. (Bot.) Consisting of, or bearing, tubers; resembling a
      tuber.
      [1913 Webster] -- Tu"ber*ous*ness, n.
      [1913 Webster]

WordNet (r) 3.0 (2006):

tuberous
    adj 1: of or relating to or resembling a tuber; "a tuberous
           root"

Moby Thesaurus II by Grady Ward, 1.0:

49 Moby Thesaurus words for "tuberous":
   botanic, bulbous, burled, cereal, farinaceous, fruitlike, fruity,
   gnarled, gnarly, herbaceous, herbal, herbose, herbous, herby,
   knobbed, knobby, knoblike, knotted, knotty, knurled, knurly,
   leguminose, leguminous, nodal, noded, nodiform, nodular, nodulated,
   noduled, nubbled, nubbly, nubby, plantlike, radicated, radiciform,
   radicular, rhizoid, rootlike, studded, torose, tubercular,
   tuberculous, tuberose, vegetable, vegetal, vegetarian,
   vegetational, vegetative, weedy