Also, an acronym for Not in Education, Employment, or Training.
In short, just as how in a modern, post-political correct world we sanitize language to say that the bomb didn't kill 50 schoolchildren, there was "collateral damage" - what we commonly would have formerly called a "worthless layabout" or "social parasite" is now just "NEET".
Obviously, not all folks who are in these circumstances are such - unless you head over to the giant waste of bandwidth and oxygen known as 4chan. To them, NEET is the ne plus ultra of life, a condition to aspire to - which is perfect. They scorn "wage-cucks" (cuck coming from "cuckold" - the idea that your time is being violated by an employer by making demands on you in exchange for renumeration) and make the usual anti-Semitic jokes about how stupid and lesser people are wage-cucks to "Mr. Shekelstein" (unquote) - toiling away for money. Meanwhile the superior beings, NEETs use their time in pursuits which they wish to engage in, instead taking money from the state or living off off well meaning parents.
Regardless as to whether these folks are serious, and not simply engaging in a wry commentary on how difficult it is to make it when graduating into a bad economy - and much of 4chan is unclear as to whether or not it's some kind of bizarre performance art or genuine, certifiable sociopathy - it's a scary meta-commentary on how life with ever-increasing rents and skyrocketing college costs make it almost more worth your time to just sit back and fail at life according to our society.
Of course, according to these threads these young men are cultivating their minds, reading poetry, cooking slow-cooked home made gourmet meals and pondering life's bigger questions - whereas based on the rest of 4chan's output, it's far more likely they're urinating into empty Mountain Dew bottles and pretending to live life on the perfect spot in the autistic spectrum where they can have contempt for "normies" (as they call them) but not be affected too badly by the bright colors and sudden violent sounds of the anime they brag about furiously masturbating to.