To spend an entire night together and not miss a single high-five.
Comes from the idea that people spending
time together
will have
fun and give each other high fives. Since the geek culture boom in the 80's, it's become much easier for a high-five to miss. If one avoids this tragic accident of pop culture, one has been said to be "five-up."
There was a
minute there when I thought Brad was going to miss my
hand, but he made it, so we were
five-up.