prost

1. simple; easy
   Odgovor je prost, samo treba malo razmisliti. — The answer is simple, you just need to think a little.
   Ovo je prosta rečenica sa jednim glagolom. — This is a simple sentence with one verb.
2. colloq. (of a person, speech) rude; vulgar; crude
   Nemoj da budeš tako prost pred decom. — Don't be so crude in front of the kids.
   Priča proste viceve na svakoj žurci. — He tells dirty jokes at every party.
3. dated (of people, social origin) common; lowly; of the common folk
   Prost narod nije mnogo mario za politiku. — The common folk didn't care much about politics.
4. (of a number) prime
   Sedam je prost broj. — Seven is a prime number.

Said of a person, "prost" usually means rude or vulgar, not simple or easy-going.