This is a high pitched noise made by your lips when they make contact and have air blown through them. The noise is similar to one farting.
It is often made when an embarresing or a ridiculous statement has been made.
Bvvvp can be used to humiliate the individual or to simply ridicule the statement.
Originated from Unionville, Canada by a group of rowdy adolescents.
Mary Anne: How's it going, Blake.
Blake Nellie: Pretty good, I just came back from pumping iron! I think I can pick up some ladies now.
Mary Anne: Bvvvp
Blake Nellie: Good one.