underguns 

The flabby gelatinous skin-mass found on the underside of post menopausal women.

"Hey dawg, did you see the underguns on Angela Landsbury on last night's episode of Murder She Wrote."

underguns by Kyle Wilkinson October 30, 2007

UnderLust 

An alternate universe of the game UnderTale containing almost everyone as lust filled monsters, and Mettaton EX as a shy talk show host.

UnderLust was created by nsfwshamecave on Tumblr.com

UnderLust by DepressingVoice16 June 28, 2016

Underbus

Verb used to describe the act of "throwing someone under the bus" or otherwise admitting someone's wrongdoing for them.

My sister was in trouble with my mom, so she underbussed me for something I did last week, and got herself off the hook.
An underbusser is a grown tattletale.

Underbus by misshappenstanc October 9, 2017

underbun

(Noun) - When a woman's buttocks pleasantly peaks out from the bottom of her respective garments.

"Dude, that mini-skirt on Tami is giving me a great shot of her underbun."

underbun by ActuallyMike December 31, 2015

Underlust 

Underlust is Au, of undertale where soul falls into the underground but its not the monster's think. So they send it to W.D Gaster to research about the soul and Gaster finds out that, He can eject the lust in monster's, And then every monster in the underground is filled with lust, Including, Toriel, Sans, Papyrus, Undyne, Alphys, Mettaton/Happstablook and Asgore, And then Asriel is in this world, Toriel and Asgore Where happy about there child and then, Asriel dies and turns in to dust, Toriel and Asgore in Sadness, The ashes of Asriel go on a flower bed and the flowers (Which where roses) made Rose and then Happstablook and Alphys meet up in a Human-Fan-Club and Sence Happstablook likes being on stage Alphys decided to build, Happstablook a Robot body (That was a Sexual related body cause of course not) And Mettaton is on stage and got tons of fans, One night though everything changed, After a show Mettaton was Sexually Assaulted and Beaten by one of his "Fans" Sence Mettaton Was badly beaten Alphys Was trying to repair Mettaton, By doing Minor repairs, and giving him glasses. And is a tad-bit shy now. And a Teen falls into the Underground to soon realize that there is sexual reference's Every where. And that where we are now.
Weapons: Toriel/Old police Batons, Sans/A ripoff of Asriel's Swords, Papyrus/Fists, Undyne/Whip, The rest of these are fists.
I'll leave the rest of the detail's to you.

Guy 1:Man, underlust makes me look like a Virgin.
Guy 2: I like underlust, although it has a sour taste its actually pretty good.

Underlust by Etp445 (Unoffical) September 17, 2020

Undergasm 

When you understand something and turns you on to the max and you cum

Dude I get it now, I think I had an undergasm

Undergasm by Ahshdbfhd November 24, 2020

undercunt 

(to) undercunt ′ʌndəkʌnt: to be less of a cunt than someone else

1. Allie was being a cunt to a coworker but ended up getting undercunted.

2. "I'm not saying you're a cunt but the other girls at the party were all undercunting you."

- "Okay, now you can really go fuck yourself, Brad!"

undercunt by alliebro August 4, 2011