A pasty jar of Shelly boi's that are sadly crushed to their death to make a delicious snack. You can but it on bread but not celery because well... that's just plain weird
Most frequently used when playing the card game Bull Sh*t (bs- other wise said badspaghetti). After the person next to you has laid their card/s down, you say peanut butter to indicate that you lied and got away with it.
Bob: (lays down cards) 3 sixes.
Dan: (lays down card) 1 seven.
Bob: Peanut butter!