A more thorough explanation:

The Wild's Case, Rule in refers to a legal rule that interprets a grant to "A and A's children" as a fee tail if A's children do not exist at the time the legal document takes effect. However, if A's children do exist at the time the legal document takes effect, the grant is interpreted as a joint tenancy.

For example, if a property owner grants their property to "John and John's children" in a legal document, and John has no children at the time the document takes effect, the property would be considered a fee tail. However, if John has children at the time the document takes effect, the property would be considered a joint tenancy.

It's important to note that this rule has been abolished in most states, along with the fee tail.