The act of intense intercourse, usually in the doggie position, where the male freefalls from a distance of 6 inches or greater into the female. Hence leaving feeling like "geronimo".
Last night that girl was so crazy, I had to give her the geronimo plunge just to satisfy her
The act of one person eating pineapple and then plunging their tongue into another’s anus
Bob: After I ate that bowl of pineapple, she asked for me to eat that ass
John: Awesome dude your first pineapple plunge!