[7/21, 12:25 PM] Baajman: Blackmail is an act of coercion using the threat of revealing or publicizing either substantially true or false information about a person or people unless certain demands are met. It is often damaging information, and may even be revealed to family members or associates. It may involve using threats of physical, mental or emotional harm, or of criminal prosecution, against the victim or someone close to the victim. It is normally carried out for personal gain, most commonly of position, money, or property.

Note:
Blackmailing is not just saying negative things about someone but also threatening and/or demanding a ransome .

EXAMPLES:
1. You need to pay my rent or I’ll leave you.

2. You need to let me move in or I’ll tell your sister what you said about her.

3.What your brother said about me is truly annoying. Unless he apologizes to me, I will tell the whole world about your family how they killed the innocent housekeeper.

That family is known for witchcraft, don't marry from there.
This was what a lady said about you to me.