Definition of "seif"

Such seifs have a somewhat zig-zag form instead of a fairly straight line.On the top of seifs small transverse dunelets are very often found, and these may be likened to almost straightened-out barchans. […] On the top of the seif they form a wave-like pattern with a fairly defined "wavelength".

1954, Bulletin of the Research Council of Israel, volume 4, page 196

Though the actual transition forms suggested in Fig. 76 do exist and have been examined by the author, the above tentative explanation of the growth of a seif dune chain should certainly not be taken as implying that all such chains have originated as barchans.

1973, Ralph Alger Bagnold, The Physics of Blown Sand and Desert Dunes, page 224

Seifs are longitudinal forms elongated parallel to the prevailing wind direction.

1980, P. Turner, Continental Red Beds, page 80

Tsoar, H. Dynamic processes acting on a longitudinal (seif) sand dune .

2009 February 26, Bruno Andreotti et al., “Giant aeolian dune size determined by the average depth of the atmospheric boundary layer”, in Nature, volume 457, number 7233, pages 1120–1123