Bad breath was the state of having malodorous exhalations.
According to Q in 2366, bad breath was one of the disadvantages to being Human. (TNG: "Deja Q")
The Vori believed that the breath of the Kradin "stinks of muck". (VOY: "Nemesis")
In 2374, after Dukat told Kira Nerys he could make things pleasant for her, she advised him to "start by doing something about your breath." (DS9: "A Time to Stand")