watermark

Etymology

water + mark

noun

1. A translucent design impressed on the surface of paper and visible when the paper is held to the light.
2. (by extension) A logo superimposed on a digital image, a television broadcast, etc.
3. (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.
4. A mark indicating the level to which water has risen.

verb

1. (transitive) To mark paper with a watermark.
2. (transitive) To mark a datafile with a digital watermark.