mlatiti

1. colloq. to beat; to thrash
   Mlatio je pesnicama po vratima. — He was pounding on the door with his fists.
   Stalno ga je mlatio stariji brat. — His older brother kept beating him up.
2. (+ instr. arms, legs) to flail; to wave about
   Dete je mlatilo nogama po vodi. — The child was thrashing his legs in the water.
   Kad priča, mlati rukama na sve strane. — When he talks, he waves his arms all over the place.
3. (of grain) to thresh
   Nekada su seljaci ručno mlatili žito. — Peasants used to thresh the grain by hand.
4. slang (mlatiti pare) to rake in money
   Otvorio je kafić i sad mlati pare. — He opened a café and now he's raking in the money.

With po + locative it means to pound on something (mlatiti po vratima).