1. To be a clearer of accusation, suspicion, implication, or the like.
2. To be an advocate and enforcer of justice.
3. To be upholder of truth in discussions.
4. To be a defender against opposition.
EX. They coudl've called the Avengers the "Vindicators", but I don't think it has the same ring to it.
"We may not be able to save the world, but we'll damn sure vindicate it," just doesn't work.