barchan (b???k??n) , barkhan , barchane or barkann (Physical Geography) a crescent-shaped shifting sand dune, convex on the windward side and steeper and concave on the leewardCollins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014