1. self-acting - Adjective
2. self-acting - Adjective Satellite
Acting of or by one's self or by itself; -- said especially of a machine or mechanism which is made to perform of or for itself what is usually done by human agency; automatic; as, a self-acting feed apparatus; a self-acting mule; a self-acting press.
Source: Webster's dictionaryself acting
a self-activating sprinkler system Source: Internet