The Collaborative International Dictionary of English v.0.48:

Tubby \Tub"by\, a.
   Resembling a tub; specifically sounding dull and without
   resonance, like a tub; wanting elasticity or freedom of
   sound; as, a tubby violin.
   [1913 Webster]

WordNet (r) 3.0 (2006):

tubby
    adj 1: short and plump [syn: dumpy, podgy, pudgy, tubby,
           roly-poly]

Moby Thesaurus II by Grady Ward, 1.0:

61 Moby Thesaurus words for "tubby":
   adipose, beefy, big-bellied, bloated, blocky, blowzy, bosomy,
   brawny, burly, buxom, chubby, chunky, corpulent, distended, dumpy,
   fat, fattish, fleshy, full, gross, heavyset, hefty, hippy,
   imposing, lusty, meaty, obese, overweight, paunchy, plump, podgy,
   portly, potbellied, pudgy, puffy, pug, pugged, pursy, retrousse,
   roly-poly, rotund, roundabout, snub-nosed, square, squat,
   squattish, squatty, stalwart, stocky, stout, strapping, stubbed,
   stubby, stumpy, swollen, thick-bodied, thickset, top-heavy,
   turned-up, well-fed, white plague