terminator

One that terminates.

The dividing line between the bright and shaded regions of the disk of a moon or planet that is illuminated by the sun.

A sequence of nucleotides that signals the end of transcription or translation and the completion of the synthesis of a nucleic acid or protein molecule.

One who or that which terminates.

In astronomy, the dividing-line between the illuminated and the unilluminated part of a heavenly body.