Flat chest 

(1) a female's upper torso with no or little curvature, having no or very small breasts;
(2) a female with such a chest, or more regularly, who is thought to have a flat chest, but actually just has A or B cups.
Usually meant as an insult or self-deprecating remark, but reclaimed by some as a source of pride and self-worth.

- "I can't believe Yuri's dating that flat chest from art class."
- "Aww, shut up. First of all, she's a beaut, and second, those are definitely B cups."

Flat chest by Monticello-W October 18, 2016

Flat-Chest Fan 

When one is extremely sexually attracted to a girl with a Flat Chest.

The term was coined from the AnimeOverlord when Ainz Ooal Gown was trying to comfort the flat chested character on the show, Shaltear Bloodfallen who was trying to fake having Big Breasts to impress him.

Mike: Damn! I like Shaltear so much!
Jonas: You're such a Flat-Chest Fan. Albedo is obviously the one for Ainz.

Flat-Chest Fan by The Original Argoniphile June 13, 2018

Flat Chest Syndrome 

Flat Chest Syndrome or Blanc Syndrome is when a girl thinks the fact that her chest is flat makes her unwanted and so becomes an ill-tempered Tsundere.

May: I think has Erika Flat Chest Syndrome.

Flat Chest Syndrome by I'm Balls Deep in your mom January 5, 2022

Flat chest energy 

a woman who is so insecure and cocky that can be broken down with a single word.
Could be used as an insult to women due to their flat chest, or to criticize a womans behaviour.

That girl is such a bitch, shes literally radiating flat chest energy

Flat chest energy by tacowithpeanutbutter11 February 4, 2023

Flat Chest Syndrome(FCS)

A phrase/ mental disorder which discribes the social immaturity displayed by women(ages 14-19) with flat chest. It's usually diagnosed by a friend or first time aqaintance who notices certain idiosynchrasies that display annoyance, or in gereral over compensation.

Victims of FCS often display narcissism, or self-centeredness; They often try to compensate by trying to be intellectually superior or catty.

It's often grown out of but the long term effects can only heal with time.

Abel- Dude (girl) is being so annoying
Chelsea- Yeah I know she must have Flat Chest Syndrome(FCS)
Abel- Oh yeah she's deffanently FCS positive.

Flat Chest Syndrome(FCS) by Chabel Roeschstraviz March 26, 2008

flat chest phoebe

when a bitch called phoebe goes up to you and roasts you so you say she has a flat chest and as she laughs you firmly grab her testicles and chest causing you to be canceled

I just did a flat chest phoebe during lunch.

flat chest phoebe by Milfhentaisenpai April 10, 2022

Noemi has a flat chest 

A fine ass latina with a flat chest.

Noemi has a flat chest, there's nothing there!

Noemi has a flat chest by Someone From CPPS December 15, 2016