Rain barrel 

To urinate into an anus with the penis inserted inside.

I heard Ted gave Susan a rain barrel for her birthday.

Rain barrel by Down Spout Jim January 16, 2022

Rain Barrel 

A fat girl that squirts

Man you should've seen Betsy last night. She is such a rain barrel.

Rain Barrel by generalofnerdia November 3, 2018

Getting rusty in the rain barrel 

Jacking off

Guy 1:Yeah last night I was Getting rusty in the rain barrel
Guy 2:Nice.

Getting rusty in the rain barrel by snubtuba November 14, 2020

tighter that a mosquito's ass stretched over a rain barrel 

Used to describe the tightness of a womans vagina to all your friends. Often used in conjuction with the words likepussy, cunt, and box. BEWARE! NEVER USE IN FRONT OF WOMEN TO DESCRIBE OTHER WOMEN. DIRE CONSEQUENCES MAY INCUR!

Her cunt was tighter that a mosquito's ass stretched over a rain barrel... niccce!

tighter that a mosquito's ass stretched over a rain barrel by Jeep_Junkie March 13, 2007

Rain-Barreling 

When an uncut male is in the shower and stretches his foreskin into a open barrel shape catching water raining down from the shower head. Creates hours of fun similar to water ballooning without the mess of urine.

Dad: why is the damn water bill so high this month.

Mom: Jimmy has discovered rain-barreling.

Rain-Barreling by Dick Onchin October 23, 2020