A person starts a search on YouTube for a specific topic or video and then clicks on a related video. Upon the completion of this video, clicks on another related video. This continues a number of times until in the end, the videos you end up watching are in no way related to your original topic of interest.
Me: I was watching some awesome videos about botfly larvae extraction last night on YouTube.
Her: Whoa! What made you want to look at those?!
Me: Well, I started out by looking up videos on fishing for muskie and before I knew it, I YouTube drifted and ended up watching these two maggots getting removed from some dude’s back. You gotta see it!