The Collaborative International Dictionary of English v.0.48:

heavyset \heavyset\ adj.
   1. obese.

   Note: usually men are portly and women are stout

   Syn: portly, stout.
        [WordNet 1.5]

   2. heavy and compact in form or build or stature.

   Syn: compact, stocky, thick, thickset.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

heavyset
    adj 1: having a short and solid form or stature; "a wrestler of
           compact build"; "he was tall and heavyset"; "stocky
           legs"; "a thickset young man" [syn: compact,
           heavyset, stocky, thick, thickset]

Moby Thesaurus II by Grady Ward, 1.0:

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