The Collaborative International Dictionary of English v.0.48:

Voluminous \Vo*lu"mi*nous\, a. [L. voluminosus: cf. F.
   volumineux.]
   Of or pertaining to volume or volumes. Specifically:
   [1913 Webster]
   (a) Consisting of many folds, coils, or convolutions.
       [1913 Webster]

             But ended foul in many a scaly fold,
             Voluminous and vast.                 --Milton.
       [1913 Webster]

             Over which dusky draperies are hanging, and
             voluminous curtains have long since fallen. --De
                                                  Quincey.
       [1913 Webster]
   (b) Of great volume, or bulk; large. --B. Jonson.
       [1913 Webster]
   (c) Consisting of many volumes or books; as, the collections
       of Muratori are voluminous.
       [1913 Webster]
   (d) Having written much, or produced many volumes; copious;
       diffuse; as, a voluminous writer.
       [1913 Webster] -- Vo*lu"mi*nous*ly, adv. --
       Vo*lu"mi*nous*ness, n.
       [1913 Webster]

WordNet (r) 3.0 (2006):

voluminous
    adj 1: large in volume or bulk; "a voluminous skirt"
    2: marked by repeated turns and bends; "a tortuous road up the
       mountain"; "winding roads are full of surprises"; "had to
       steer the car down a twisty track" [syn: tortuous,
       twisting, twisty, winding, voluminous]
    3: large in number or quantity (especially of discourse); "she
       took copious notes"; "a subject of voluminous legislation"
       [syn: copious, voluminous]