Gladstone Geyser Share definition Flag When you have a female fill her mouth with diet coke and pop a mentos right before fellatio. Dude she gave me a Gladstone Geyser last night, I had to call a cleaning company to handle the mess, but it was so worth it! Gladstone Geyser by Mahogany Mauler August 11, 2025 Get the Gladstone Geyser mug.