Threenup 

A marriage between 3 people. Primarily when a person joins into marriage with a married couple. Two out of the three can remain married if any decides to divorce.

If this is going to work, we need a threenup...
That threesome was so good we should look into a threenup

Threenup by Chainsdragon June 7, 2019

Threenut 

Noun: Three Nuts

"I slept with this guy last night. It wasn't great, he had a threenut

Threenut by Gayassbitch420 December 5, 2020

threenut 

a peanut which contains 3 nuts inside one shell

I found a rare threenut hiding inside the Texas Roadhouse peanut barrel

threenut by Arkyst May 28, 2021