Threatens to reveal embarrassing or damaging information about someone to force them to pay money or do what the blackmailer wants.
From blackmail (16th-century Scots, 'black mail' = illegal extortion) + -s (third-person singular). The term evolved from literal protection money to any coercive threat.
In the digital age, blackmail has exploded through 'sextortion' — criminals hack intimate photos and threaten to share them, making this ancient crime trivially easy through technology.
Complete word intelligence in one call. Free tier — 50 lookups/day.