noun A translucent design impressed on the surface of paper and visible when the paper is held to the light.
noun A logo superimposed on a digital image, a television broadcast, etc.
noun 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.
noun A default hint caption displayed in a text box prior to the user inputting any text.
noun A mark indicating the level to which water has risen.