Dictionary:

smutch

  (smŭch)

To soil or stain.

A stain or spot of dirt.

[Perhaps alteration of SMUDGE.]

verb

To make dirty: befoul, begrime, besmirch, besoil, black, blacken, defile, dirty, smudge, soil, sully. See clean/dirty.

noun

A discolored mark made by smearing: blot, blotch, daub, smear, smirch, smudge, splotch, stain. See marks.

The verb has one meaning:

Meaning #1: make a smudge on; soil by smudging
  Synonyms: smear, blur, smudge