ETYM Pref. re- + trace: cf. French retracer. Related to Retract.
1. To trace back, as a line.
2. To go back, in or over (a previous course); to go over again in a reverse direction.
3. To trace over again, or renew the outline of, as a drawing; to draw again.

The path followed by the electron beam in a raster-scan computer monitor as it returns either from the right to the left edge of the screen or from the bottom to the top of the screen. The retrace positions the electron beam for its next sweep across or down the screen; during this interval, the beam is briefly turned off to avoid drawing an unwanted line on the screen. Retracing occurs many times each second and uses tightly synchronized signals to ensure that the electron beam is turned off and on during the retrace. See also blanking, horizontal retrace, raster display, vertical retrace.