Fleece or blackmail people by taking advantage of their weakness or under a certain pretext.

以某种借口或利用某人的弱点，索取钱财或抬高价格。

youdao

She started off by accusing him of blackmail but he more or less ignored her.

她以指控他敲诈勒索开始，但他基本上没理会她。

《柯林斯英汉双解大词典》

So go ahead and tell them a secret, your deepest feelings, or anything they can use against you as blackmail.

所以，不要再犹豫了，告诉她你的秘密，你内心深处的感觉，或者其它什么她可以用了勒索你的事情。

youdao

Besides stealing electronic cash, a thief could exploit stored data for mischief - or blackmail.

CNN: ASIANOW - Asiaweek

Unlike oligarchs in emerging economies, Wall Street's financiers do not use overt bribery or blackmail.

ECONOMIST: The financial crisis and the future of regulation

In the old days they would have to have a carefully cultivated agent, an American motivated by money, ideology or blackmail, in place to steal sensitive information.

BBC: IMF cyber attacks signal new spying era