Medicine. Of a disease: hidden, concealed, difficult to detect; unaccompanied by readily discernible signs or symptoms; spec. designating a primary…

Of the nature of systole (systole, n. 2); of or relating to systole; occurring during systole.

Physiology. Of the heartbeat, breathing, or other physiological process: recurring at regular intervals, periodic. Cf. rhythm, n. 3.

Physiology. = rhythmic, adj. 2c.

Physiology. Concerned in bodily actions or processes which are independent of the will.