In the simplest of definition, a man child is an immature guy who just refuses to grow up. This doesn't mean he necessarily lives at home with mom and dad ― although he probably should considering the way he functions in the real world ― but that he just doesn't have his life together.
“Hey man what is a man child
“Go watch Erobb221, Lime
by GradualMist April 03, 2021
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A man that expects a woman to support him financially. Somehow always forgets his wallet at home.
Man child wants the ladies to take him on a date.
by Rica Spice August 17, 2018
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(Australian context) A boy who goes through puberty at a very young age, and is usually the tallest and oldest looking amongst his peers between the ages of 11-13. After that, he stops growing, and his peers go through puberty and become the same size/taller than him in the later teenage years. Despite this, however, a manchild will retain his characteristically mature features well into later life.
twelve year old boy1: dude, that guy over there has already started shaving. And he's like taller than all of us.

twelve-year old boy2: Yeah, he's such a man child!

(4 years later)
16-year old boy1: Hey look, it's the same guy we were calling a manchild 4 years ago! What happened man, he used to be taller than all of us, now he's like 5'9.5'' and we're all 6'1'' !!

16-year old boy2: I know, he's actually the same size he was when he was 12. But dude, he's still a manchild- look at his awesome stubble and hairy arms!
by AusDesi August 14, 2009
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a grown man who is very immature, therefore considered a man child.
Dude you need to grow up and stop being such a man child
by rhoni March 06, 2005
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A man by age but a child in mentality and actions. Usually an inability to get over the "frat boy" or "party boy" phase. Can't have fun without a beer; oftentimes brews his own beer. Still relate to women as sex objects (even in they're married) and are emotionally undeveloped (e.g., fight for their rights mentality even if there is nothing worth fighting; rarely takes responsibility for own failings). A general irritant to women and men that have matured.
Facebooking about brewing beer and gross bodily functions is typical of a man child.
by Agulowok February 20, 2010
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A man child is a male who is over the age of 25, who still lives as though he is a juvenile. Many man-children are not gainfully employed, and survive off of the financial support of their enabling parents. Heavy video-game addiction to fantasy games such as World of Warcraft are key to the man-child.
"You'll never believe it, but that 30-year old uber-gamer man child who lives door to me finally got a job!"
by MarcusI December 18, 2007
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