It's basically what it sounds like: you put your tongue on someone's eyeball.
For many teens, eyeball licking is the new "second base" and comes after making out.
But it's not just teens; adults are using "worming" as a type of foreplay.
Because as you might have guessed, tonguing someone's eye can have some medical repercussions.
One possible explanation for the new fad is this year-old music video from the Japanese band Born, which features some prime eyeball licking at 3:35.