n. pl., but sing. or pl. in usage 1. physical exercises performed in a sustained and strenuous fashion designed to cause a temporary increase in respiration rate and heart rate, such a running, swimming, walking, or calisthenics. Calisthenic sessions in groups, performed by following a leader in moving to a rhythmic musical accompaniment, are a popular form of aerobics. [ PJC. ]
2. a system of physical conditioning relying largely on aerobics exercises. [ PJC. ]