1. When your hairdresser/friend/parent/self absolutely destroys your hair by cutting/styling/coloring/burning/perming it incorrectly.
2. The awkward silence that follows the question, "how do you like my new hairdo?"
1. Did you see Kate and her hairror? She let the cosmetology students color it and now it's chartreuse green!
2. Girl: "Baby, how do you like my new style?"
Guy: *silence* "Uh...*gulp*...it's...umm...."
Random third party bystander: "A hairror!"
When somebody is said to have a horror of a hairstyle, it is a hairor. It is a hairstyle that, when viewed by unsuspecting eyes, causes bloodloss of the eyes and an urge to attack the hairror with scissors or a lawnmower.
Donald Trump is a hairror. Mullets. Richard Simmons.