terminator

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

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

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

Harriot, looking at the moon, saw the irregular terminator, the highlights and shadows, the mountain ranges and valleys that Galileo had described – and he also convinced himself that he saw Galileo's imaginary crater.

A DNA sequence that causes RNA transcription to cease and an mRNA transcript to break off.

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