One who gives someone else the power to behave in a certain way.
One who or that which helps something to happen.
One who encourages a bad habit in another (typically drug addiction) by their behaviour.
One who knowingly allows himself or herself to be used for another's profit; a dupe.
A magician's assistant who pretends to be a member of the audience.
A confederate; a person who is secretly working for the researcher, unknown to the study participant.
A straight man.
A secret informant for police.
To act as a straight man.