leading edge

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun Nautical The edge of a sail that faces the wind.
• noun The front edge of an airplane propeller blade or wing.
• noun The foremost position in a trend or movement; the vanguard.
• noun Someone or something occupying such a position.

from the GNU version of the Collaborative International Dictionary of English.

• noun (Aeronautics) the front edge of an airfoil; same as advancing edge, above.
• noun the front edge of anything that moves; also used metaphorically, . See also cutting edge.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun aeronautics The frontmost edge of a wing or other airfoil of an aircraft; sometimes contains slots or slats
• noun by extension The foremost part of a trend etc; a vanguard
• noun At the forefront of practice or technology, contrast with bleeding edge

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun forward edge of an airfoil