When a song you haven't heard for a while gets stuck in your head for no apparent reason. It can be an entire song, or a simple lyric or guitar riff. It then plays repetitively in your head to almost no end for a random amount of time. It can be a beloved song, or a loathed song.
It's been ages since I've heard Sir-Mix-A-Lot, but I've been suffering from Randoriffia today. I've been humming "Baby Got Back" and saying "L.A. face with an Oakland booty" non-stop all morning. Now my co-workers are getting concerned.