(1):

(n.) The shortening of the long syllable.

(2):

(n.) The contraction of the heart and arteries by which the blood is forced onward and the circulation kept up; - correlative to diastole.

(3):

(n.) The contraction of the heart and arteries by which the blood is forced onward and the circulation kept up; also, the contraction of a rhythmically pulsating contractile vacuole; - correlative to diastole.