nightmare

A nightmare is a very bad dream or experience that makes you feel scared, anxious, or unhappy.

You might be thinking, "Wait, isn't a nightmare just something I have in my sleep?" And yes, it's true - a nightmare can be a frightening dream that happens while we're asleep. But the word 'nightmare' is used more broadly than that. For example, if you're working on a project and everything seems to be going wrong, you might say, "This job is turning into a nightmare!" It means the experience is causing you a lot of stress or trouble. You can also use the word to describe a situation that's difficult to handle, like trying to deal with a mean boss or navigating through heavy traffic on a busy road. In all these cases, 'nightmare' describes an unpleasant or overwhelming situation that feels almost as bad as having a scary dream while you're asleep.