Nightmare Before Christmas Music Box Unbelievable. Uncover the meanings behind your nightmares with our guide to common bad dreams. A nightmare is a disturbing dream that provokes a strong negative emotional reaction.

Uncover the meanings behind your nightmares with our guide to common bad dreams. Learn about nightmares, their causes, & how to reduce. A nightmare, also known as a bad dream, [1] is an unpleasant dream that can cause a strong emotional response from the mind, typically fear but also.