When one's nipples and breast tissue is hypersensitive to tactile manipulation by another person—most likely due to extra nerve endings in these areas—thereby creating a heightened sense of pleasure and arousal.
Darnell: "Yo, I was smashin this chick out last night right, but all the bitch wanted me to do was suck on her titties!"
Bartholomew: "She musta had mad Sensititity, son."
Matt: "Why the fuck does your girl have metal plating on all her bras man??"
Kyler: "Cuz dude, she's got a severe case of Sensititity and if something touches her nips she'll have an uncontrollable orgasm right there in public.