origin: an allusion to Democritus, "The Laughing Philosopher" from Abdera, city of ancient Thrace= Abdēra + -ian
adjective
The Joker, Goofy, Schmedley, and possibly an annoying coworker or family member all have one thing in common -- they laugh incessantly, so much so that it's foolish, for they are no longer reacting to actual stimuli, it's more of a knee-jerk response; absurd; inclined to compulsive merriment.
example: Based on the abderian laughter emanating from the kitchen, we knew mother had been at the cooking sherry again.