Under Tongue 

The fatty tongue under your real tongue. If you have a "fatty mouth" you most likely have an Under Tongue.
Mouths with under tongue are usually better when giving oral.

My girl has an Under Tongue so you know that head is on point.

Under Tongue by StefVonE December 1, 2022

Under the tongue 

A person who is subservient in the relationship based purely on sexual intercourse. They will do anything if it means getting more sex.

Similar to: Under the thumb.

Tony: "Where is Alex?"

Matt: "He's not out tonight. He's totally under the tongue by his new girlfriend"

Tony: "Too busy having sex to come hang with the guys!"

Under the tongue by Gregtron January 23, 2011

undertongue 

Historically known as "the vagina of the mouth," this area has gained recent popularity among "headventurers" for remaining constantly wet and sensitive.

Headventurer:"Sheila, lets try something new"

Sheila: "oh ya, put it in my undertongue"

undertongue by Gorilla Adam December 6, 2009

Undertongue 

1. (n): Area on the bottom of the tongue where the tongue attaches to the rest of the mouth. (You know what i'm talking about- it's all veiny and full of saliva)

Girl: "I was picking my teeth with a toothpick and I slipped and stabbed my undertongue today!"

Guy: "Wow. You impaled your undertongue? Gross."

Undertongue by K Floss December 6, 2009

undertonguer

The title given to a person with a severe lack of tongue action during kissing . We’re talking less than sub 20% tongue to kiss ratio. Refer to overtonguer.

She’s a total undertonguer ... she needs to get more movement happening, it’s like kissing a mannequin

undertonguer by Chippawood April 13, 2019