pokretač

1. (of a person) initiator; originator
   On je bio pokretač cele inicijative. — He was the initiator of the whole initiative.
   Ko je pokretač ove peticije? — Who started this petition?
2. (of a factor or phenomenon) driving force; driver
   Turizam je glavni pokretač lokalne privrede. — Tourism is the main driver of the local economy.
3. (of a machine) starter; starting device
   Stari motor ima ručni pokretač, pa se pali na kanap. — The old engine has a manual starter, so you start it with a pull cord.

In the sense of initiator it usually takes the genitive: pokretač promena. A car starter is usually called anlaser in everyday speech and elektropokretač in technical language; bare pokretač is rare in this sense.