klošar

1. colloq. derog. tramp; bum; vagrant
   Na klupi u parku spava neki klošar. — Some tramp is sleeping on a bench in the park.
2. colloq. derog. good-for-nothing; bum
   Obuci se pristojno, izgledaš kao klošar. — Dress decently, you look like a bum.

The word is disparaging; the neutral term for a homeless person is beskućnik.