Source : Webster's Revised Unabridged Dictionary (1913)

Besmut \Be*smut"\, v. t. [imp. & p. p. {Besmutted}; p. pr. & vb.
   n. {Besmutting}.] [Pref. be- + smut: cf. AS. besm[=i]tan, and
   also OE. besmotren.]
   To blacken with smut; to foul with soot.