The vagina version of the game Chubby Bunny (seeing who can fit the most marshmallows in their mouth while still being able to say "chubby bunny").It is the act of inserting more than 1 tampon into a vagina at one time.
"I was so fucked up last night that this morning I realized I had accidentally played a game of chubby beaver, and I won."
"All of my tampons keep disappearing, someone must be training for the chubby beaver olympics"