Pattern of Scanning Lines Made by an Electron Beam
Puzzle 2 of At the Ballet Hard Pack
Question is: Pattern of Scanning Lines Made by an Electron Beam
and the answer is: RASTER
Word Meaning:
RASTER — (electronics) A scanning pattern of parallel lines that form the display of an image projected on a cathode-ray tube of a television set or display screen.
Definitions from Wiktionary.