prljati

1. to dirty; to soil
   Nemoj da mi prljaš tepih blatnjavim cipelama! — Don't get my carpet dirty with your muddy shoes!
2. (prljati se) to get dirty
   Deca se stalno prljaju dok se igraju u parku. — The kids keep getting dirty while playing in the park.
3. (of name, reputation) to sully; to tarnish
   Takvim izjavama samo prljaš ime svoje porodice. — With statements like that you're only tarnishing your family's name.

The perfective is uprljati or zaprljati.