a person who is not a police officer but who tries to catch and punish criminals.
Source: Merriam-Webster's Learner's Dictionary. Examples:
Sep 9, 2008
Sep 28, 2016
In the Wild West
a member of a self-appointed group of citizens who undert... Meaning, pronunciation, example sentences, and more from Oxford Dictionaries.
Members: Angela Ford, David Jenkins ...
An outlaw who punishes lawbreakers personally and illegally instead or relying
on the inadequate law enforcers of society. A