Simple Definition:

Halitosis refers to a condition characterized by persistent bad breath [a smell coming from the mouth that is unpleasant]. It is often caused by poor oral hygiene, certain foods, or underlying health issues. For example, if a person consistently has a foul odor [bad smell] coming from their mouth even after brushing and using mouthwash, they may be experiencing halitosis.

Very Simple Definition:

Halitosis means having bad breath because of a medical reason. If someone’s breath smells unpleasant even after brushing their teeth, they may have Halitosis.