1. past tense of blackjack; to hit or strike (someone) with a blackjack (a weapon consisting of a heavy head on a handle)
Usage: transitive verb; informal
2. past tense of blackjack; to coerce or force (someone) into doing something against their will
Usage: transitive verb; informal

Examples

• The security guard was blackjacked during the robbery.
• He was blackjacked into signing the contract by threats.
• The victim was blackjacked and left unconscious.
• They blackjacked him into compliance with their demands.
• The officer reported being blackjacked by an unknown assailant.