Many popular definitions of OPP include:
Other People's Property
Other People's Privates
Other People's Penis
Other People's Pussy
but in a VH1 presentation of the 100 Greatest Hip Hop Songs, Treach of Naughty by Nature states
"OPP can stand for anything, the first O is Other and the second P is People's but the last P can stand for anything."
Stands For Other Peoples Pussy/Other Peoples Penis
It is asking the listener if he/she is willing to have sexual relations with a person who is known to already have a boyfriend or girlfriend.
"OPP For The Guys:It's sorta like another way to call a cat a kitten
It's five little letters that are missin' here"
"OPP For The Ladies:The first two letters are the same but the last is something
different
It's the longest, loveliest, lean-- I call it the leanest
It's another five letter word rhymin' with cleanest and meanest"