Someone who terminates or ends something, especially (in later use) an assassin or exterminator.

(computing) A text character or string that serves to mark the end of a document or transmission.

(astronomy) The line between the day side and the night side of a moon, planet or other celestial body.

(biochemistry) A DNA sequence which causes RNA transcription to cease and an mRNA transcript to break off.

(electronics) An electrical device that absorbs reflection at the end of a transmission line.

(science fiction) An intelligent android created to destroy humans.