leading edge 
noun
1 Aeronautics The foremost edge of an aerofoil, especially a wing or propeller blade. Compare with trailing edge.Their lengthened nacelles overlapped the leading edge of the wing and were equipped with a streamlined canopy and cabin in which a single gunner was installed....
- There was a hole in the leading edge of the wing, six inches from the propeller.
- On this clean surface, the full-size wing was drawn with the leading edge, trailing edge, spars, and ribs all correctly located.
2The forefront or vanguard, especially of technological development: [as modifier]: leading-edge research...
- Growing a leading-edge technology business in a turbulent economic climate takes guts.
- They go on to point out, correctly, that they are unequipped to make judgments on the relative scientific merits of two highly qualified candidates in a leading-edge research field.
- The goal is to allow it to develop the leading-edge chip solutions it needs going forward more cheaply than if the group's various member companies maintain their own semiconductor operations.
3 Electronics The part of a pulse in which the amplitude increases.Unless stated otherwise, Qn and Qp are measured at the leading edge of the test pulse.