A bagina is where 5 people are included in a sexual act. They usually put a bag over one of the male's heads and sexually pleasures him, usually by arousing him. Then a female puts her vagina over the male's penis and had sexual intercourse. Each female in the group of 5 takes their turn, and then it switches to the next male (if any). Lara's Orgasm may be related to this sexual act.
John: Hey Carl, how was the bagina last night?
Carl: The bagina was very nice, they put a bag over my head and many vaginae went on my nice hard dick!