Quiz: Remember the definition of mal de mer?


[nap] /næp/
Geology. a large mass of rock thrust a considerable distance along a nearly horizontal fault plane or in an overturned anticlinal fold.
Geometry. one of the two equal sections of a cone.
1905-10, Americanism; < French: literally, tablecloth, cloth; Old French nappe, nape < Latin mappa; cf. napkin Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2015.
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Examples from the web for nappe
  • If the upper nappe profile remains the same as it was while fully ventilated, the weir has sufficient ventilation.
  • Free flow occurs when a thin-plate weir allows free access of air under the falling jet sheet or nappe.
  • Consequently, the nappe does not contract from the width of the channel.
  • The height of pullup behind the nappe depends upon the drop, discharge, and crest length.
  • The weir should be ventilated, if necessary, to prevent a vacuum from forming on the underside of the nappe.
  • The shape is intended to match the underside of the nappe at its upper extremities.
  • For gravity flow inlets with square-edged or gated orifices, the nappe created by inflow at the orifice entrance shall be vented.
  • The stream of water leaving the weir crest is called the nappe.
  • For gravity flow inlets with square edge or gated orifices, the nappe created by inflow at the orifice entrance should be vented.
  • Air should circulate freely both under and on the sides of the nappe.
British Dictionary definitions for nappe


a large sheet or mass of rock, commonly a recumbent fold, that has been thrust from its original position by earth movements
the sheet of water that flows over a dam or weir
(geometry) either of the two parts into which a cone (sense 2) is divided by the vertex
Word Origin
C20: from French: tablecloth
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
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