A play on the English writer J.K. Rowling's (writer of the Harry Potter Series) name. It usually means "Just kidding, and I am laughing aloud at the same time" or just "I am currently laughing aloud".
Frank: Dude you're such an asshole sometimes, you know Sarah and I broke up last week.
Joe: I was J.K. Lolling (insert emphasis here).
Joe: I was J.K. Lolling (insert emphasis here).
by Baeowulf February 21, 2008