breath sound [AS, braeth + L, sonus] , the sound of air passing in and out of the lungs, as heard with a stethoscope. Vesicular, bronchovesicular, and bronchial breath sounds are normal. Decreased breath sounds may indicate an obstruction of an airway, collapse of a portion or all of a lung, thickening of the pleurae of the lungs, emphysema, or other chronic obstructive pulmonary disease.
