The act of staying in your room for days at a time, not showering, and avoiding
social interaction to the point of becoming a greasy, unhealthy slob. Usually accompanied by heavy use of the internet and/or video games. A fermenter's natural habitat is typically found in the dark corners of sites like 4chan, reddit, and twitch.
Once you start to ferment, it can be hard to get out, usually requiring some sort of
wake-up call from the outside world. Some fermenters never get this wake-up call or ignore it, resulting in a lifetime spent mostly in their rooms.
Fermentation can lead to later complications such as depression, anxiety, anti-sociality, obesity, diabetes, and more.
Example:
Friend 1: Hey man, were gonna see a movie tonight, wanna come?
Friend 2:
Nah dude, I gotta rank up on League of Legends, I'm gonna pass this time.
Friend 1: Bro you've been playing that game for three days straight, you're
fermenting dude!
Friend 2: Shit man, you're right. Imma
take a shower and join y'all