One complete horizontal sweep of an electron beam in a cathode ray tube, or a single row of addressed pixels in a matrix display. Video signals transmit images sequentially by drawing them scan line by scan line from top to bottom. In analog video, the time it takes to trace one line dictates the horizontal sync frequency.
Heard on the job
The monitor has a vertical deflection issue, you can see the scan lines bunching up at the top of the tube.
Related terms
Cathode ray tube
A vacuum tube containing one or more electron guns and a phosphorescent screen used to display images.
HSYNC
The horizontal synchronization pulse that tells a display to start drawing a new line.
CRT
A cathode-ray tube is a vacuum envelope containing an electron gun and a phosphorescent screen.