A person who goes along to a social situation to buffer the awkwardness. Used often when you're trying to get to know someone, but certainly not in the "date" sort of way. Works best if the awkward buffer is a friend of both parties.
Bob: I'm going to meet Maria tonight so we can hang out and get to know each other. Could you come with and be an awkward buffer?
Shelly: Sure! I'm good friends with her, I'll help keep the conversation going :)