Source : Webster's Revised Unabridged Dictionary (1913)

Befoul \Be*foul"\, v. t. [imp. & p. p. {Befouled}; p. pr. & vb.
   n. {Befouling}.] [Cf. AS. bef?lan; pref. be- + f?lan to foul.
   See {Foul}, a.]
   1. To make foul; to soil.

   2. To entangle or run against so as to impede motion.

Source : WordNet®

befoul
     v : spot, stain, or pollute; "The townspeople defiled the river
         by emptying raw sewage into it" [syn: {foul}, {defile}, {maculate}]