What term refers to the act of breathing out?

The term that refers to the act of breathing out is "exhalation." This process involves the release of air from the lungs through the respiratory tract, clearing carbon dioxide from the body. Exhalation occurs as part of the respiratory cycle, which includes inhalation (breathing in) followed by exhalation.

Inhalation, the second option, involves drawing air into the lungs and is the counterpart to exhalation. Ingestion relates to the intake of food and drink rather than air and is unrelated to the respiratory process. Insufflation, while it does involve blowing air or gas into a body cavity for medical purposes, doesn't pertain specifically to the standard act of breathing out. Therefore, exhalation is the correct term for the act of breathing out.