systole

1. (physiology) The rhythmic contraction of the heart, by which blood is driven through the arteries.Examples: "[…] I did almoſt beleeve, that the motion of the Heart vvas knovvn to God alone: For neither could I rightly diſtinguiſh, vvhich vvay the Diaſtole and Systole came to be, nor vvhen nor vvhere the dilation and conſtriction had its exiſtence."; "A double systole catapulted him into full consciousness again, and he promised his uncorrected self that he would limit his daily ration of cigarettes to a couple of heartbeats."; "There is no essential virtue in comfort. To be relaxed is good if it is part of a process of systole and diastole. Relaxation comes between phases of tenseness."

2. (prosody) A shortening of a naturally long vowel.

3. (mathematics) The shortest noncontractible loop on a compact metric space.

4. (biology) The contraction of the contractile vesicles in certain algae, plasmodia, and zoospores.