The Collaborative International Dictionary of English v.0.48:

Fatten \Fat"ten\, v. t. [imp. & p. p. Fattened; p. pr. & vb.
   n. Fattening.] [See Fat, v. t.]
   1. To make fat; to feed for slaughter; to make fleshy or
      plump with fat; to fill full; to fat.
      [1913 Webster]

   2. To make fertile and fruitful; to enrich; as, to fatten
      land; to fatten fields with blood. --Dryden.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

fattened \fattened\ adj.
   fed until grown and ready for slaughter or for sale in the
   market; -- of market animals.
   [WordNet 1.5 +PJC]

WordNet (r) 3.0 (2006):

fattened
    adj 1: (of market animals) made ready for market