An instance where a statement is made about one's mom, and is immediately followed by a "your mom" joke. In such a case, a "double yourmomitive" has occurred and therefore cancels the said "your mom" joke. The original statement about one's mom, however, is still valid.
Little Billy and 2 of his friends, Little Joey and Little Bobby, are playing at the playground. Billy says, "I think my mom is hot!", which Joey immediately follows by saying, "Your mom thinks your mom is hot." As you can see, unless Joey is making a reference to Billy's mom being vain, this is clearly a "double yourmomitive" and should bee accordingly and promptly stricken from the record.