To tell an outlandish lie with no factual basis whatsoever usually with the intention to destroying an opponent usually used in connection with an overbearing abusive semi deranged older female in a position of feigned authority.
It is believed that this word derives from the word jail bait. It applies though to an older woman not a young girl. The root of the issue is the same though -- a female who is dangerous through deception, deceit, and manipulation.
Another theory is that this word derives from an old Amazon word Juuber which meant a very tall, masculine, evil, dangerous woman who kills and eats men and also children. In the deepest jungles, when a man is really upset because at an older woman, he will shout "Juuber." This is considered an obscenity in the Amazon Jungle.
That old Joubert hag lied stating that I had sex with a goat; gee whiz, I live in New York City and have never seen a goat.
Lanette, stop acting like a Joubert.