A Big Johnny is when a girl is being gang-banged by two men; one penis in her mouth and the other in her vagina. If both men come simultaneously, she then pulls the penises out so that they ejaculate on each other's penises.
I was in a threesome once and we did a Big Johnny. My dick was sticky for three whole days.
Noun. Specifically the name for whatever waste comes out of ones anus. Can be singular or plural. This is something my dad and his family would say, going well back before WWII and in Pennsylvania and New York.
I ate about 30 candy bars in an hour. Then I had really nasty bigjohns.