A sexual act in which a male alternates between inserting his penis in a woman's anus and vagina specifically when the woman is menstruating. Fecal matter deposited on the penis is referred to as the "Peanut Butter" due to its thick brown appearance and menstrual secretions are attributed to be the "Jelly" due the pasty red residue resembling strawberry jam. For added effect this act can be performed to the song with the same name, "Peanut Butter Jelly Time."
I heard the "Peanut Butter Jelly Time" song the other day and I had a sudden urge for some real Peanut Butter Jelly Time! My girlfriend just happened to be menstruating so I called her over for some good old fashioned fun. Things got rather messy but boy was it worth it!