Systole: The time period when the heart is contracting. The period specifically during which the left ventricle of the heart contracts.

The final letter in "systole" is pronounced as a long "e" as in "lee." The adjective for systole is systolic.

The systolic pressure is specifically the maximum arterial pressure during contraction of the left ventricle of the heart.

In a blood pressure reading, the systolic pressure is typically the first number recorded. For example, with a blood pressure of 120/80 ("120 over 80"), the systolic pressure is 120. By "120" is meant 120 mm Hg (millimeters of mercury).

A systolic murmur is a heart murmur heard during systole, the time the heart contracts, between the normal first and second heart sounds.

"Systole" came without change from the Greek systole meaning "a drawing together or a contraction." The term has been in use since the 16th century to denote the contraction of the heart muscle.