The Collaborative International Dictionary of English v.0.48:

Obese \O*bese"\ a. [L. obesus eaten away, lean; also, that has
   eaten itself fat, fat, stout, p. p. of obedere to devour; ob
   (see Ob-) + edere to eat. See Eat.]
   Excessively corpulent; fat; fleshy.
   [1913 Webster]

WordNet (r) 3.0 (2006):

obese
    adj 1: excessively fat; "a weighty man" [syn: corpulent,
           obese, weighty, rotund]

Moby Thesaurus II by Grady Ward, 1.0:

50 Moby Thesaurus words for "obese":
   adipose, beefy, big-bellied, bloated, blowzy, bosomy, brawny,
   burly, buxom, chubby, chunky, corpulent, distended, dumpy, fat,
   fattish, fleshy, full, gross, heavy, heavyset, hefty, hippy,
   imposing, lusty, meaty, overweight, paunchy, plump, podgy, portly,
   potbellied, pudgy, puffy, pursy, roly-poly, rotund, square, squat,
   squatty, stalwart, stocky, stout, strapping, swollen, thick-bodied,
   thickset, top-heavy, tubby, well-fed