URL: 

wave equation

1. n. [Geophysics]

A mathematical expression to represent wave displacement and wave velocity (V) as functions of space (x, y, z) and time (t).

2ψ = ∂2ψ/∂x2 + ∂2ψ/∂y2 + ∂2ψ/∂z2 = (1/V2) ∂2ψ/∂t2,

where
ψ = wave displacement
V = wave velocity
x, y and z = space coordinates
t = time.