Crummy means bad, unpleasant, or of poor quality. When your day feels crummy, everything seems to go wrong: you might oversleep, forget your homework, and lose at recess. A crummy old shed has peeling paint, a sagging roof, and cobwebs in every corner.

The word captures that feeling of disappointment and low quality. A crummy excuse is one nobody believes. Crummy weather means cold rain or gloomy skies. When you're sick, you feel crummy: tired, achy, and miserable.

People often use crummy for things that aren't terrible but definitely aren't good. A sandwich might not be spoiled, just crummy: stale bread, wilted lettuce, and not much flavor. A crummy movie isn't scary or offensive, just boring and poorly made.

The word has a casual, everyday feeling to it. You probably wouldn't write “crummy” in a formal essay, but you might absolutely tell your friend, “I had a crummy morning.” It's a perfect word for when something is genuinely disappointing but not worth making a big fuss about.