Bathtub turtle Share definition Flag When your stomach and penis float to the surface of the water in the tub, resembling a sea turtle popping its head up. I have to remember to knock next time before I see another bathtub turtle. Bathtub turtle by Kurtjohnson February 24, 2024 0 0 Get merch Get the Bathtub turtle mug. Buy Now — $32.95 See more merch