  Extreme Ultraviolet (EUV) waves have been found for about 15 years. However,
significant controversy remains over their physical natures and origins. In
this paper, we report an EUV wave that was accompanied by an X1.9 flare and a
partial halo coronal mass ejection. Using high temporal and spatial resolution
observations taken by the {\em Solar Dynamics Observatory} and the
Solar-TErrestrial RElations Observatory, we are able to investigate the
detailed kinematics of the EUV wave. We find several arguments that support the
fast-mode wave scenario: (1) The speed of the EUV wave (570 km/s) is higher
than the sound speed of quiet-Sun corona. (2) Significant deceleration of the
EUV wave (-130 m/s2) is found during its propagation. (3) The EUV wave resulted
in the oscillations of a loop and a filament along its propagation path, and a
reflected wave from the polar coronal hole is also detected. (4) Refraction or
reflection effect is observed when the EUV wave was passing through two coronal
bright points. (5) The dimming region behind the wavefront stopped to expand
when the wavefront started to become diffuse. (6) The profiles of the wavefront
exhibited a dispersive nature, and the magnetosonic Mach number of the EUV wave
derived from the highest intensity jump is about 1.4. In addition,
triangulation indicates that the EUV wave propagated within a height range of
about 60-100 Mm above the photosphere. We propose that the EUV wave observed
should be a nonlinear fast-mode magnetosonic wave that propagated freely in the
corona after it was driven by the CME expanding flanks during the initial
period.
