The female version of "joint at the dick."
When two friends think extremely similarly and often do things similarly or
even at the same
time without being aware of it. The two
may seem practically related and will often claim that "great minds think alike," but everyone knows that they're truly joint at the uterus.
Unbiological sisters.
Boy: "Why is it that you two
always seem to text me around the same
time?"
Girl: "We're just joint at the uterus."