Short for boyfriend.
"Chrissy, your boif is a geek."
"I'd like you to meet my new boif."
When pockets of air get trapped under one of the many rolls of fat of an obese person, the release of that air and the sound it makes is a Boif. Much like a similar phenomenon that occurs in a woman's vagina, the queef.
you fucked that fat girl?! how loud did she boif man?