1. In baseball, when two consecutive batters each hit a home run.
2. The act is sitting back-to-back with someone, while giving each other reach-around manual stimulation.
1. "Dude, I went to the Orioles game last night and Roberts and Markakis hit back-to-back jacks!"
"What was the final score?"
"They lost 10-2."
2. Tom and Kevin had some drunken back-to-back jacks last night, claiming it's not gay if they can't see what they're doing
This is one of the most difficult sexual positions and it's approved by Dr. Falchi as "corona safe" you are back to back doing it - you have to be very flexible.
We did the double back jimmy jack last night and my legs are killing me, I need to do more yoga.