1. The act of ejaculating while the penis is completely pancaked between a pair of breasts so that the cum is contained between them, hence a filling a bun with cream. Often a less messy alternative to the pearl necklace or facial. Requires either gigantic breasts or a smallish penis.
Afraid that he might ruin Leslie's makeup, Jon smothered his dick between her DDDs as he began to cum, cream-bunning her like a gentleman.