When you fall asleep watching YouTube only to find the next day that you've ended up on a different channel you don't even recognize. This is usually the result of leaving autoplay on.
Matthew: Dude, I was YouTube Sleepwalking last night...
Chris: Really?
Matthew: Yeah. I was watching a let's play. When I woke up, my phone was playing some porn video!
by ThatInternetDweller February 13, 2017
Get the YouTube Sleepwalking mug.