naizmeničan

1. alternating; alternate
   U kući imamo naizmeničnu struju od 230 volti. — We have 230-volt alternating current at home.
   Posle naizmeničnih kiša i sunca došlo je pravo leto. — After alternating rain and sun, real summer arrived.

The adverb naizmenično ("in turns, alternately") is more frequent than the adjective.