The person that shows you around when you're new to a community; called the icebreaker because they usually help avoid awkwardness by starting small-talk.
Person 1: Who's that new girl? Person 2: I have no idea. All I know is that Mary is playing icebreaker for her.
When a stoner mixes cocaine and weed which gives it the same effect of an icebreaker. (the combination of white and green)
Jim: Weed just hasn't been doin it for me lately...
Stan: have u ever made yourself an icebreaker?
Jim: No, but good idea, that'll fuck me up!!