A water gap is a pass or gorge through which a river flows, cutting across a mountain ridge or other resistant rock formation. Water gaps are significant in geomorphology for understanding the history of river incision, the evolution of drainage systems, and the tectonic activity in a region.
Reference: Oberlander, T. M. (1965). “The Zagros Streams: A New Interpretation of Transverse Drainage in an Orogenic Zone.” Syracuse Geographical Series, No. 1.