The Collaborative International Dictionary of English v.0.48:

Putrefy \Pu"tre*fy\, v. t. [Written also putrify.] [imp. & p. p.
   Putrefied; p. pr. & vb. n. Putrefying.] [F. putr['e]fier;
   L. putrere to be rotten + -ficare (in. comp.) to make; cf. L.
   putrefacere. See Putrid, and -fy.]
   1. To render putrid; to cause to decay offensively; to cause
      to be decomposed; to cause to rot.
      [1913 Webster]

   2. To corrupt; to make foul.
      [1913 Webster]

            Private suits do putrefy the public good. --Bacon.
      [1913 Webster]

            They would but stink, and putrefy the air. --Shak.
      [1913 Webster]

   3. To make morbid, carious, or gangrenous; as, to putrefy an
      ulcer or wound.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Putrefy \Pu"tre*fy\, v. i.
   To become putrid; to decay offensively; to rot. --Isa. 1. 6.
   [1913 Webster]

WordNet (r) 3.0 (2006):

putrefy
    v 1: become putrid; decay with an offensive smell; "organic
         matter putrefies"

Moby Thesaurus II by Grady Ward, 1.0:

31 Moby Thesaurus words for "putrefy":
   break down, break up, canker, corrupt, crumble, crumble into dust,
   decay, decompose, deteriorate, disintegrate, fall into decay,
   fall to pieces, fester, gangrene, go bad, go off, go to pieces,
   mildew, mold, molder, mortify, moulder, necrose, putresce, rankle,
   rot, sphacelate, spoil, suppurate, taint, turn