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]