All the points just reached by a wave as it propagates.
2.
(physics) an imaginary surface joining all points in space that are reached at the same instant by a wave propagating through a medium. Synonym:wavefront.
... plain, suppose the front of a surface of waves of any sort to be striking an object which resists them. If an organ of sense is placed in the resisting object, it will judge the direction of the waves or the direction of the object producing them by a line at right angles with the wave front. Now suppose a body is placed between the body producing the waves and the sensitive organ. The waves must go around this body and will produce an eddy behind it, so that the wave front will have a different direction, ... — Scientific American Supplement, No. 401, September 8, 1883 • Various
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