I. ˈrastə(r) noun
( -s )
Etymology: German, from Latin raster, rastrum rake, mattock, from radere to scrape, rake, shave — more at rat
: the area upon which the image is reproduced in the cathode-ray tube of a television set
II. noun
: a pattern for scanning an area from side to side in lines from top to bottom
an electron beam in a cathode-ray tube scans the phosphor screen in a raster
also : a pattern of closely spaced rows of dots that form the image on a cathode-ray tube (as of a television or computer display)