The yellow-brown stains that collect on the armpits of a shirt. It can occur on any type of shirt, but primarily refers to white v-neck undershirts, as worn by the prophet Al Bundy.

Anatidaephobia is defined as a pervasive, irrational fear that one is being watched by a duck. The anatidaephobic individual fears that no matter where they are or what they are doing, a duck watches.

Anatidaephobia is derived from the Greek word "anatidae", meaning ducks, geese or swans and "phobos" meaning fear.