I. ˈ ̷ ̷ ̷ ̷ˌ ̷ ̷ noun
Etymology: water (I) + mark
1. : a mark indicating the height to which water has risen or at which it has stood or is expected to stand : waterline ; especially : tidemark
2. : a marking in paper resulting from differences in thickness usually produced by pressure of a projecting design in the mold or on the dandy roll and visible when the paper is held up to the light ; also : the design or the metal pattern producing the marking — compare impressed watermark
II. transitive verb
1.
a. : to mark (paper) with a watermark
b. : to impress (a given design) as a watermark
2. : to determine the watermark on (a stamp) usually for philatelic purposes