obrtaj

1. (of an engine, wheel) revolution; rotation
   Motor radi na tri hiljade obrtaja u minutu. — The engine runs at three thousand revolutions per minute.
   Na autoputu drži niske obrtaje. — On the motorway he keeps the revs low.
2. turn; spin
   Vrata su se otvorila posle dva obrtaja ključa. — The door opened after two turns of the key.
   Plesačica je napravila savršen obrtaj. — The dancer did a perfect spin.

For an unexpected twist of events, obrt is usually used.