A reference to the character in Left for Dead 2, who usually has an expressionless face. If someone would have no expression on their face they would be "coach faced".
Man: "My girlfriend had a Coach Face during sex last night, apparently my dong is too small".
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.