blackmail

Short definition from Wiktionary

Noun

1. 1
   The extortion of money or favors by threats of public accusation, critique, or exposure.
2. 2
   Compromising material that can be used to extort someone.
3. 3
   Compromising material that can be used to extort someone: A type of roleplay where the submissive shares information that may be exploited by the dominant.
4. 4
   A form of protection money (or corn, cattle, etc.) anciently paid, in the north of England and south of Scotland, to the allies of robbers in order to be spared from pillage.
5. 5
   Black rent; rent paid in corn, meat, or the lowest coin, as opposed to white rent, which was paid in silver.

Verb

1. 1
   To extort money or favors from (a person) by exciting fears of injury other than bodily harm, such as injury to reputation, distress of mind, false accusation, etc.
2. 2
   To speak ill of someone; to defame someone.