Definition of "watermark"

A translucent design impressed on the surface of paper and visible when the paper is held to the light.  examples

(by extension) A logo superimposed on a digital image, a television broadcast, etc.  examples

(computing) A value stored in a datafile to ensure its integrity, so that if the file's contents are changed then the watermark will no longer match the contents.  examples

A mark indicating the level to which water has risen.  examples

(transitive) To mark paper with a watermark.  examples

(transitive) To mark a datafile with a digital watermark.  examples