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.
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.