A portmanteau of the word Hikikomori (a Japanese word used to describe people who isolate themselves and lack a social life) and the acronym NEET; "Not in Education, Employment or Training."
"Get off your ass and go look for a job! Quit being such a hikiNEET."
Someone who has withdrawn from all real-life social interaction. A hikikomori rarely leaves their home, and has no friends or family with whom they interact. A hikikomori is NOT always an otaku, nerd, gamer, etc, though they can be.
Sneak away to meet your mistress. ("Hiking the Appalachian Trail" is the first explanation of where South Carolina Gov. Mark Sanford was when he disappeared.)
"Has anyone seen Jawann? I've been calling and texting him for three days and he's not answering."