/ ˈblækmeɪl; NAmE / noun , verb
■ noun [ U ]
1.
the crime of demanding money from a person by threatening to tell sb else a secret about them
2.
the act of putting pressure on a person or a group to do sth they do not want to do, for example by making threats or by making them feel guilty :
emotional / moral blackmail
■ verb
[ vn ] blackmail sb (into doing sth) to force sb to give you money or do sth for you by threatening them, for example by saying you will tell people a secret about them :
She blackmailed him for years by threatening to tell the newspapers about their affair.
The President said he wouldn't be blackmailed into agreeing to the terrorists' demands.
••
WORD ORIGIN
mid 16th cent. (denoting protection money levied by Scottish chiefs): from black + obsolete mail tribute, rent , from Old Norse mál speech, agreement.