The Collaborative International Dictionary of English v.0.48:

Unimaginative \Unimaginative\
   See imaginative.

WordNet (r) 3.0 (2006):

unimaginative
    adj 1: deficient in originality or creativity; lacking powers of
           invention; "a sterile ideology lacking in originality";
           "unimaginative development of a musical theme";
           "uninspired writing" [syn: sterile, unimaginative,
           uninspired, uninventive]
    2: dealing only with concrete facts
    3: lacking spontaneity or originality or individuality;
       "stereotyped phrases of condolence"; "even his profanity was
       unimaginative" [syn: stereotyped, stereotypic,
       stereotypical, unimaginative]

Moby Thesaurus II by Grady Ward, 1.0:

68 Moby Thesaurus words for "unimaginative":
   Spartan, arid, ascetic, austere, bald, bare, barren, candid,
   common, commonplace, direct, dry, dull, earthbound, flat, frank,
   homely, homespun, humdrum, infecund, infertile, insipid, lean,
   literal, matter-of-fact, mundane, natural, neat, open, ordinary,
   pedestrian, plain, plain-speaking, plain-spoken, poetryless,
   prosaic, prose, prosing, prosy, pure, rustic, severe, simple,
   simple-speaking, sober, spare, staid, stark, stolid,
   straightforward, stuffy, tiresome, unadorned, unaffected,
   unembellished, unfanciful, unideal, unidealistic, unimpassioned,
   uninspired, uninventive, unoriginal, unpoetic, unpoetical,
   unromantic, unromanticized, unvarnished, vapid