Source : Webster's Revised Unabridged Dictionary (1913)

Dirty \Dirt"y\, v. t. [imp. & p. p. {Dirtied}; p. pr. & vb. n.
   {Dirtying}.]
   1. To foul; to make filthy; to soil; as, to dirty the clothes
      or hands.

   2. To tarnish; to sully; to scandalize; -- said of
      reputation, character, etc.

Source : WordNet®

dirtying
     n : the act of soiling something [syn: {soiling}, {soilure}]