Small spots or marks of light appearing on a radar screen, or metaphorically small, temporary problems or events.
Possibly onomatopoetic, imitating the sound of radar signals. Emerged as technical jargon in WWII and became common in general English by the 1950s.
Radar 'blips' saved countless lives in WWII, and the term spread to pop culture—every alien spaceship in sci-fi films needs to show as mysterious blips on radar, making the word essential to the genre.
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