Water flounder \Wa"ter floun"der\ (Zo["o]l.) The windowpane ({Pleuronectes maculatus}). [Local, U. S.] Windowpane \Win"dow*pane`\, n. 1. (Arch.) See {Pane}, n., (3) b . [In this sense, written also {window pane}.] 2. (Zo["o]l.) A thin, spotted American turbot ({Pleuronectes maculatus}) remarkable for its translucency. It is not valued as a food fish. Called also {spotted turbot}, {daylight}, {spotted sand flounder}, and {water flounder}.