Watermark

['wɔːtəmɑːk] or ['wɔtɚmɑrk]

(noun.) a distinguishing mark impressed on paper during manufacture; visible when paper is held up to the light.

Typist: Marietta--From WordNet

(n.) A mark indicating the height to which water has risen, or at which it has stood; the usual limit of high or low water.

(n.) A letter, device, or the like, wrought into paper during the process of manufacture.

(n.) See Water line, 2.

Checker: Roland