Stuffy describes air that feels stale, warm, and hard to breathe, like a classroom on a hot afternoon when all the windows are closed. A stuffy room lacks fresh air and makes you want to throw open a window or step outside. Basements, attics, and crowded spaces often feel stuffy, especially in summer.

The word also describes people who act overly formal, serious, or uptight. A stuffy person might insist on strict rules at a casual party or correct everyone's grammar during a friendly conversation. They care too much about manners, traditions, or “proper” behavior and forget to relax and have fun. If someone calls a museum or ceremony stuffy, they mean it feels too formal or boring, like everyone's afraid to laugh or speak naturally.

You might also have a stuffy nose when you're sick and can't breathe easily through your nostrils. Just like a stuffy room needs fresh air, a stuffy nose needs to clear out so you can breathe normally again.