Lousy means very bad or of poor quality. When something is lousy, it's disappointing, unpleasant, or just plain terrible. A lousy day might include forgetting your lunch, failing a test you studied for, and getting caught in the rain. A lousy meal tastes awful. A lousy movie bores you from start to finish.

Today people almost always use it to describe anything unpleasant or inferior. You might feel lousy when you're sick with a cold, meaning you feel miserable and uncomfortable. A lousy excuse is weak and unconvincing, like blaming your dog for eating homework you never actually did.

Lousy carries a feeling of genuine disappointment or disgust. It expresses strong frustration or dissatisfaction, going beyond mild criticism. When you call something lousy, you mean it's seriously bad. The weather isn't just cloudy, it's lousy because it ruined your outdoor plans. The service at a restaurant wasn't just slow, it was lousy because the staff seemed not to care at all.