  In this paper we prove the local well-posedness (LWP) for the 3D compressible
Euler equations describing the motion of a liquid in an unbounded initial
domain with moving boundary. The liquid is under the influence of gravity but
without surface tension, and it is not assumed to be irrotational. We apply the
tangential smoothing method introduced in [10,11] to construct the
approximation system with energy estimates uniform in the smooth parameter. It
should be emphasized that, when doing the nonlinear a priori estimates, we need
neither the higher order wave equation of the pressure and delicate elliptic
estimates, nor the higher regularity on the flow-map or initial vorticity.
Instead, we adapt the Alinhac's good unknowns to the estimates of full spatial
derivatives.
