The act of pushing on a skateboard with the wrong foot. If you skate goofy (with your right foot forward,) then you would push mongo if you pushed w/ your right foot. Depending on where you go, mongo pushing is either accepted, or hated. Many beginner level skaters push mongo, so some people see it as the mark of a poseur or a noob.
Someone who jumps from one relationship immediately into another one.
Serial monogamists can not stand to be alone and often suffer from vast commitment and insecurity issues.
Because they jump into relationships immediately after the previous one has ended, serial monogamists typically don't take the time to reflect on their behavior or why their previous relationships failed; thus, they end up making the same relationship mistakes over and over again.
Person 1: Damn, Dustin already has a new girlfriend?! It's only been two weeks since he broke up with his fiance! I think he's a sociopath.