WordNet (r) 3.0 (2006):

thumbprint
    n 1: fingerprint made by the thumb (especially by the pad of the
         thumb)

Moby Thesaurus II by Grady Ward, 1.0:

40 Moby Thesaurus words for "thumbprint":
   boss, bump, colophon, concavity, convexity, dactylogram,
   dactylograph, dent, dint, embossment, excrescence, fingerprint,
   footmark, footprint, footstep, fossil footprint, ichnite,
   ichnolite, impress, impression, imprint, indent, indentation,
   indention, lump, pad, paw print, pawmark, pimple, print, pug,
   pugmark, seal, sigil, signet, stamp, step, stud, thumbmark,
   vestige