Sort of like a gap year, combined with a geek year and a leap year because its a very long and geeky gap year taken by a Free Open Source Software (FOSS) developers to focus on FOSS development full-time. Usually crowd funded, or something done by engineers with rather large bank balances after cashing in their options.
Random Frat Dude at a data science Meetup: "So, what do you do?". FOSS Programmer: "Me, I'm taking a Geep Year!" Random Frat Dude: "Oh cool dude, what are you working on?" FOSS Programmer: "oh you know, saving the world, fixing the ridiculous NTLM v1.0 password hash problem." Random Frat Dude: "Wow cool dude, what's your GitHub sponsors page or do you have a GoFundMe?"