cavity definition
A cavity is a carved-out space inside something solid like a wall or a tooth. If you have a cavity, you have a hole in your tooth, and itâs time to go to the dentist for a filling. Lucky you. Doctors sometimes refer to various internal body parts as cavities, such as the abdominal cavity, which includes the stomach and other hollow parts of the abdomen. You are more likely to hear the word at the dentistâs office, when she finds a cavity, which is a space in your tooth that's been eaten away by decay.