Definition of watermarks:
(n) :
A translucent design impressed on the surface of paper and visible when the paper is held to the light.
(n) :
(by extension) A logo superimposed on a digital image, a television broadcast, etc.
(n) :
A mark indicating the level to which water has risen.
(v) :
(transitive) To mark paper with a watermark.
(v) :
(transitive) To mark a datafile with a digital watermark.
(n) :
(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.