An entail is when someone can't sell their property because they have to pass it down to someone else. It's often used for big houses or lands.
If you think of an heir as a person who gets something after someone dies, then "entail" makes sense. When you promise that some land will go to your children or grandchildren when you die, you're entailing it to them. This can happen in wills, but often people just talk about it like a promise between family members. It's not as common as selling property, but it happens when families want to keep things within the family for generations.
(transitive) To imply, require, or invoke.
Example: This activity will entail careful attention to detail.
