a downward stroke, as of a machine part, piston, or the like.
a downward stroke in writing, often heavier and darker than an upward stroke.

Origin of downstroke

First recorded in 1850–55; down1 + stroke1 Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for downstroke

Historical Examples of downstroke