terminator

American  

[tur-muh-ney-ter] / ˈtɜr məˌneɪ tər /

noun

1. a person or thing that terminates.

2. Astronomy. the dividing line between the illuminated and the unilluminated part of a satellite or planet, especially the moon.

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terminator British  

/ ˈtɜːmɪˌneɪtə /

noun

1. the line dividing the illuminated and dark part of the moon or a planet

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Etymology

Origin of terminator

1760–70; < Late Latin terminātor, equivalent to terminā ( re ) to terminate + -tor -tor

Example Sentences

Artemis II pilot Victor Glover heard the call of the terminator: the border between the moon’s daytime and nighttime — the lunar dawn.

From Los Angeles Times • Apr. 9, 2026

That frontier between light and darkness is known as the terminator.

From BBC • Apr. 3, 2026

At the highest possible end, a comparable would be Mathieu van der Poel, the Dutch terminator who has won Tour stages, one-day classics like Paris-Roubaix and turns up for races in a Lamborghini.

From The Wall Street Journal • Feb. 16, 2026

Further data will be needed to confirm with certainty that this intriguing excess of light on the eastern terminator of WASP-76b is a glory.

From Science Daily • Apr. 5, 2024

Looking at it, it is perfectly clear that the terminator is irregular, but this irregularity is what information scientists call ‘noise’: it makes no sense and conveys no information.

From "The Invention of Science" by David Wootton