šišati

1. (+ acc.) to cut someone's hair
   Frizerka me šiša već deset godina. — The same hairdresser has been cutting my hair for ten years.
   Tata sam šiša sina mašinicom. — Dad cuts his son's hair himself with clippers.
2. (šišati se) to get a haircut
   Šišam se svakog meseca kod istog berberina. — I get my hair cut every month at the same barber's.
3. (of sheep, hedges) to shear; to trim
   Na selu se ovce šišaju u proleće. — In the village, sheep are sheared in spring.
   Komšija svake subote šiša živu ogradu. — Our neighbour trims the hedge every Saturday.
4. slang (ne šišati koga) to not give a damn about someone; to ignore
   Pričam joj satima, a ona me ne šiša. — I talk to her for hours, and she doesn't give a damn.

The perfective is ošišati; "to get a haircut" is šišati se.