Someone who is seemingly emotionless in person, but always posts online with a lot of excitement (a lot of exclamation marks, all caps, etc.)
Jennifer, being very internetaverted, sat quietly in Starbucks, eyes glued to her phone, without so much as a polite smile on her face while posting to Facebook, "OMG!!! HE PROPOSED TO ME!!! I'M GETTING MARRIED, EVERYBODY!!!!!! AAAAAAAAHHHHH!!!!!!!!"
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.