When a girl gives you a hand job using both hands. Fist the right up the shaft then the left....repeat. Kind of like milking a cow only there is only one teat.
When a couple decide to take their relationship further, with both parties shitting in a bathtub, and then one partner receives anal sex in the reverse cowgirl position. Like riding a boat.
Much like the motorboat, except you take a runny shit on the woman's chest first. You then proceed to motorboat her, and every few seconds you lift your head up and yell "Mark Twain!"