The Collaborative International Dictionary of English v.0.48:

Lummox \Lum"mox\, n.
   A fat, ungainly, stupid person; an awkward bungler. [Low.]
   [1913 Webster]

WordNet (r) 3.0 (2006):

lummox
    n 1: an awkward stupid person [syn: lout, clod,
         stumblebum, goon, oaf, lubber, lummox, lump,
         gawk]