terminator
noun
ter·mi·na·tor ˈtər-mə-ˌnā-tər 
1
: the dividing line between the illuminated and the unilluminated part of the moon's or a planet's disk
2
: one that terminates
Example Sentences
Recent Examples on the Web If may even have been possible to see sliver of frost on the M0on’s terminator—the divider between sunlight and darkness (so, day and night) —though no humans were around at the time. 
Jamie Carter, Forbes, 21 May 2022 Kyle Guy is a 6-1, 167-pound terminator on the court. Gregg Doyel, The Indianapolis Star, 12 May 2022 The first set of HIV drugs were nucleic acid inhibitors, known as chain terminator drugs. William A. Haseltine, Scientific American, 1 Oct. 2020 Most observers prefer to study the moon when the line between light and dark (called the terminator) is visible, because the deep shadows there make crater rims and walls on the line pop in relief. Nicole Clausing, Sunset Magazine, 24 Sep. 2020 Underwood possessed a terminator-like focus during that time. Murphy Wheeler, The Indianapolis Star, 16 June 2020 Young John and the new terminator break Sarah Connor out of the mental hospital. Eliana Dockterman, Time, 1 Nov. 2019 And heads certainly turned as Jerry Rowe stomped around the Indiana Convention Center in his larger-than-life terminator costume. Emily Sabens, Indianapolis Star, 3 Aug. 2019 But two very familiar faces — those of the original terminator (Arnold Schwarzenegger) and Sarah Connor (Linda Hamilton) also return to join in on the fun. Andrew R. Chow, Time, 7 Aug. 2019 See More
Jamie Carter, Forbes, 21 May 2022 Kyle Guy is a 6-1, 167-pound terminator on the court. Gregg Doyel, The Indianapolis Star, 12 May 2022 The first set of HIV drugs were nucleic acid inhibitors, known as chain terminator drugs. William A. Haseltine, Scientific American, 1 Oct. 2020 Most observers prefer to study the moon when the line between light and dark (called the terminator) is visible, because the deep shadows there make crater rims and walls on the line pop in relief. Nicole Clausing, Sunset Magazine, 24 Sep. 2020 Underwood possessed a terminator-like focus during that time. Murphy Wheeler, The Indianapolis Star, 16 June 2020 Young John and the new terminator break Sarah Connor out of the mental hospital. Eliana Dockterman, Time, 1 Nov. 2019 And heads certainly turned as Jerry Rowe stomped around the Indiana Convention Center in his larger-than-life terminator costume. Emily Sabens, Indianapolis Star, 3 Aug. 2019 But two very familiar faces — those of the original terminator (Arnold Schwarzenegger) and Sarah Connor (Linda Hamilton) also return to join in on the fun. Andrew R. Chow, Time, 7 Aug. 2019 See More Word History
First Known Use
1652, in the meaning defined at sense 2