riverboat 

A MPV (multi purpose vehicle) that (unlike most of them) can actually cross muddy fields, ford every stream, climb every mountain etc.

Darrin's new Probe is a real riverboat but it has a shitty gearbox

riverboat by poodlewrestler August 30, 2005

riverboat gambler 

alludes to one who takes undue risk, wagering on the outcomes of inconsequential events and activities either for money or out of compulsion

Sylvester bet me that the next automobile to pass on Route 66 would be a turquoise Chevy Colorado. He is a riverboat gambler.

riverboat gambler by HeadsIwinTailsulose March 5, 2015

riverboat style hand job 

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.

My girlfriend asked me if I wanted a regular or riverboat style hand job.

riverboat style hand job by Bobby Poppe September 17, 2006

Egyptian Riverboat 

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.

Hey Babe, wanna take a trip on the Egyptian Riverboat?

Egyptian Riverboat by FatWillysSurfShack June 16, 2016

Memphis Riverboat 

When a person goes in for a Cleveland Steamer and hits your belly instead... And goes on to churn the result like a Riverboat

Big gay Dennis went in for a tiajuana backpack, but lost his footing and ended up with a jelly belly which he turned into a Memphis Riverboat

Memphis Riverboat by Cunbunal December 16, 2017

Mississippi Riverboat 

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!"

Shari wanted me to give her a Cleveland Steamer, but I gave her an extra treat when when I gave her a Mississippi Riverboat instead!

Mississippi Riverboat by Crablouse April 21, 2009

Mississippi Riverboat 

When you are fucking a girl doggie style and you put your thumb in her ass to steer the direction of the motion

She was pulling away so i had to mississippi riverboat her ass back on track

Mississippi Riverboat by humandumpster May 10, 2010