An image, sound, or other thought (usually one that you
don'
t want to think about) that gets stuck in your mind. The
best way to get rid of a brainworm is to replace it with something else (just
don't think about your current stuck thought, though).
A brainworm is different from an earworm in that an earworm is a song that gets stuck in your head, while a brainworm is anything that gets stuck in your head.