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Someone who is 25 or older and still shows no interest in joining the real world. Often living at home for little or no rent, these people usually avoid any form of responsibility whatsoever. They also get increasingly resentful as life passes them by and wonder why their friends and family never truly treat them with the respect they believe they deserve for the achievements in life that they haven't actually got.

Often showing exceptional interest in computer games, tabletop games, movies and sci-fi shows. These individuals truly do not want to grow up. They don't realise you can enjoy all of these things in a super geeky fashion while also having a job, a car and possibly a girl/boyfriend. They simply focus all their attention into their hobbies and lose sight of the world around them.

Not bad, or malicious people necessarily. Just due to the way they've been raised, or the way they've dealt with the world. These people are probably going to live at home till they're 50. They often don't manage to settle down with members of the opposite sex for several reasons, usually a combination of poor self-esteem, poor self-management and the fact that they blame everyone else for their less than stellar existence. Most women/men find this highly unattractive and hence the adult child generally stays single either forever or until they finally do something about their situation and change their life. Some adult children occasionally meet other adult children and hook up. The majority of the time, both individuals will be massively obese, both suffer from depression and both stay at home all day while on sickness benefits. (because they're too depressed/lazy/fat to work) Likelyhood of their residence smelling of shit and unwashed clothes is high.

For the rest that never change and wish things will change without them putting the effort in. They will remain the same - they are truly lost.
"Wow, I wish Gary would come out but he never has any money because he spends his whole months income on Dungeons and Dragons books and Xbox games." He is an adult child.

"I wish I could learn to drive but I just can't afford lessons or manage the responsibility of driving. Ooo, what's that? Collectors edition of World of Warcraft for £70? I MUST BUY IT!"
by TheManWhoKnows February 27, 2009
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An Adult Child is someone who goes their own way. They're not against society, being married with children nor having a full time job, but for some mysterious reason unknown to mankind they are a natural happenstance. They just happen. Happy little big people just golly walking about.
An Adult Child is someone unknown to mankind. The little person asks the big person"what are you gonna get up to today Billy" ? "ah I'll probably just go golly walkin about town and try save my mind" Like Billy, they are extremely sensitive beings and only wishes well for their mind and at the same time for the world. They don't tend to forget about the unimportant important things in life and also not themselves therefore anybody else. It's merely to a point of no return, when in not just some but in all cases they do return but then it's as if there's this other big little them wanting to take over their stuff and not wanting them to play as children but wants them to play as these little big grown-ups. These little big themes however isn't them and for the most part they just confuse people like Billy, who just wanted to play in the Sun, under the Stars and the Moon just as children would play but alas they're apparently adults now.
by Chutnell January 31, 2019
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Someone who is an adult (over 18) but still displays child-like features and characteristics. They feel as if they still are a child and don't want to grow up yet, spirit wise.
Johnathan and Samantha would rather play video games and go go-kart racing than go on sit-down dates at fancy restaurants. Thus, they are adult children.
via giphy
by KingKidnem September 16, 2017
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