Boosy could be used as a way to call someone a pussy, could be used to call someone a dumbass or retard. Boosy is mainly used as a shortened version of boosy peach, but also has a different meaning. That meaning being female genitalia.
"You hear John backed down from that fight yesterday?"
"Man, hes such a boosy."
"eat my boosy"
Boosy peach can be used as another way for calling someone a dumbass/retard.
"Johns being a real boosy peach right now"