Getting your next relationship set up before dumping your current S/O. Generally involves
cheating (at least emotionally) on your current partner with the intended future partner. Refers to playing on the monkeybars, where you
don't let go of the first
bar until you've grabbed on the second.
Bill: "Well, your
brother just sent the Save The Dates for his third
marriage - they haven't even finalized the divorce yet!"
Joe: "Yeah, the monkey branching SOB did the same for his second
marriage as well - all his relationships 'overlap,' if ya know what I mean."
OR
Joe: "Sue and I decided to try an open relationship."
Bill: "I dunno, sounds like she's monkey branching to her *next* relationship."