Definitions for daymareˈdeɪˌmɛər
Random House Webster's College Dictionary
a distressing experience, similar to a bad dream, occurring while one is awake.
Origin of daymare:
1730–40; day+ (night )mare
A terrifying experience, having the characteristics of a nightmare, during wakefulness
Origin: From day and nightmare
a kind of incubus which occurs during wakefulness, attended by the peculiar pressure on the chest which characterizes nightmare