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:

Fatten \Fat"ten\, v. i.
   To grow fat or corpulent; to grow plump, thick, or fleshy; to
   be pampered.
   [1913 Webster]

         And villains fatten with the brave man's labor.
                                                  --Otway.
   [1913 Webster]

WordNet (r) 3.0 (2006):

fatten
    v 1: make fat or plump; "We will plump out that poor starving
         child" [syn: fatten, fat, flesh out, fill out,
         plump, plump out, fatten out, fatten up]