somebody who constantly interrupts people, constantly yells stupid and unnecessary things, irritates the hell out of you, has the stupidest opinions about everything, has no life, doesn't know how to have fun, is abstinent to drugs/alcohol for no fucking reason, thinks that being cool is being a dick, doesn't know how to talk to women, is perverted, has no respect for women, stares at women's body parts directly with no subtly or shame, will NEVER get laid without paying for it, is arrogant, condescending, and in general pisses everybody off.
In other words, one of those guys who are just straight up losers in every single way and think they are right about, synonym for loser, faggott, bitch, or hard-headed douche bag.
NOBODY likes somebody that is a moonster. LITERALLY nobody.
"yea seriously, hell never get laid"
"or have any friends for that matter...."
"I just dont understand people like him, seriously wtf"
" I know, somepeople are just destined to be losers."
"imagine him in 10 years, living alone, jacking off to porn, doing nothing on friday and saturday nights, no friends.... wow, I kinda of feel sad for him."
"we call him a moonster for a reason, no joke man"