grown-ass adult 

A person who is legally and biologically in the adult stage of human development. Typically used as a derisive term for a person who acts way, way younger than they actually are, i.e. a manchild.

Oh, for the love of God, you're a grown-ass adult. Do your own damn laundry!

grown-ass adult by Intelligence001 February 12, 2020

Millennium adult 

An adult who was born in the new millennium (Born on January 1, 2000 or later). Typically, someone born in the new millennium becomes a millennium adult when he or she reaches the age 18 (In most countries).

Scott to Mom: Hey mom.
Mom to Scott: Hey my baby, happy birthday! I can't believe you're 17 you are growing up so fast!
Scott to Mom: Actually mom....I'm 18.
Mott to Scott: Wait, no you aren't.

Scott to Mom: Yes I am mom. I was born in 2000, not 2001.

Mom to Scott: Oh no...my baby is a millennium adult (vomits)_
Scott to Mom: Are you alright mother?

Millennium adult by MexicanJunior April 23, 2018

SUB-ADULT 

Sub-adult: People between the age group of 18 and 24ish that are technically or kegally adults, but have no clue how to Adult.

Jay, the sub-adults need money again for school and I had to help them with scheduling their school break and getting plane tickets. One day the will actually be able to do something on their own, I hope!!

SUB-ADULT by Tabago's mom April 6, 2019

Underage Adult 

A child who is mentally, physically or emotionally mature. Or a grown-up, legally of age who is not physically, emotionally or mentally mature.

I was an underage adult when I asked a 40 year old man for a kiss.

Underage Adult by Netta Y January 10, 2022

a Michigan adult 

someone who lives in Michigan and is 14 and 8 months old (in Michigan a 14 and 8-month-old can drive and work)

person a: wow they look a little young to be driving and working

person b: don't worry they're a Michigan adult

person a: weird

a Michigan adult by thicckiid January 10, 2021

Harry Potter Adult 

A millennial adult, with or without kids, that can't stop talking about Harry Potter, including the books, the movies, and the theme park lands - particularly Diagon Alley - at Universal Studios/Islands of Adventure in Orlando, Florida. Even if they do have kids, they're still way more obsessed with Harry Potter than their kids ever would be. They probably engage in casual Harry Potter cosplay and visit the theme park lands at least once a year, and/or at your local town or city's weekly or monthly Harry Potter trivia night. They are obsessed with everything Harry Potter, including, but not limited to, basing their entire personality and/or identity revolving around their "official Hogwarts House"; oversharing way too many photos of them in Harry Potter cosplay; being obsessed with Harry Potter trivia; building a massive Harry Potter collection to rival that of comic book, toy/action figure, and anime/manga nerds; having Harry Potter-themed rooms in their house; and/or probably having at least one Harry Potter-themed tattoo. One of the most bizarre and weird people you'll ever encounter, and also probably somewhere on the autism spectrum.

"That Harry Potter Adult over there won't stop talking about how much of the Hufflepuff they are, and showing off their tattoo of Cedric Diggory."

Harry Potter Adult by Aleitheia August 22, 2022

Young Adult Fiction 

A genre of (primarily) novels, movies, and tv shows that often focuses on the perspective of a young teen protagonist who is a goody two-shoes mary sue messianic type of character who lives in a dystopian setting and for some reason he/she is the leader of a rebellion against a totalitarian government or uncovers a government conspiracy and seeks out to liberate the people of his/her dystopian nation. Often this is a cheap way of writing a story because the intended audience are tween age kids, teenagers, and even college students because people of these age groups are easily impressed with narrow story telling and narratives that play with their sense of grandiosity.

It becomes worse with another form of Young Adult Fiction that focuses on romantic angst and (even worse) romantic angst with fantasy monsters like vampires, zombies (ehhh necrophilia!), and werewolves (that's for furries). Many of these romantic YA novels tend to focus on bland and 1 dimensional characters with extremely bizarre scenarios of drama or teen angst that are supposedly "relatable" but are really far fetched from being relatable to a irl person. Once again tween and teenage female readers tend to read this stuff because it somehow relates to their trivial problems when in reality they don't at all.

Examples of Young Adult Fiction in the science fiction dystopian setting:
The Hunger Games, Divergent, Ender's Game, Maze Runner.
Examples of Young Adult Fiction with romantic drama or romantic drama with halloween monsters:
Twilight, Paper Towns, Fault of Our Stars, Warm Bodies, A Hunger Like No Other, and lastly, Fifty Shades of Gray.

Young Adult Fiction by Deadmojo September 2, 2018