let one 

To expel flatulence; to fart.

Hey, dude, didja let one just a moment ago? Man, I could smell your cheezer a mile away!

let one by pentozali August 28, 2006

let one's hair down

(verb) to relax; to behave informally.

Letcho hair down, dog!

let one's hair down by Fangsta March 18, 2003

Let one fly 

Another way of saying fart, let one rip or let one tear

Jimmy just let one fly and it smells like a pile of rotting parsnips

Let one fly by samstorm December 5, 2004

let one go 

To do a fart

Gee dude, is that the drains or did you just let one go?

let one go by David from Kingsbury December 27, 2003

Let one out

To go and jack off one time

Aight imma go let one out now.

Let one out by Gorosei December 17, 2019

let one slip 

To shoot someone.
With a gun.
Fool.

Pull out the 9.
Pop in the clip.
And let one slip....
Into these crazy fools

let one slip by RicHARD September 23, 2003

Let one tear 

Another way of saying fart, let one rip or let one fly

Jimmy let one tear and it smelt of a rotting pile of cabbage.

Let one tear by samstorm December 5, 2004