n. A derivative of the "motorboat" in which one places one's lips and cheeks against the vagina, then shakes the head from side to side, keeping the lips slack, so as to produce a "bu-bb-br-br-bb-bur-bu-ber" sound.
(See also: motorboat)
She said she'd seen and done it all, and nothing I did could surprise her -- but then I put on my best Sean Connery and gave her the submarine.