My girlfriend was getting all hot and wet when I was rubbing her clit and then her booty juice got mixed with her pussy juice and created a tasty mixture of bootussy juice.
When Maggie walked into the party. Scarlett winced and said "Girl!, I smell Bootassy! Where you been bitch?" Maggie replied "I have been on my sexual odyssey with that hunky man I am dating."
A combination of the stink of a booty and the fishy smell of a pussy. Generally used to describe a rather foul smelling woman who has not bathed for several days or weeks.