Definitions for "S-wave"
A secondary, or shear, body seismic wave that travels through the depth of the Earth. S-waves can only be transmitted by solids.
The secondary wave, traveling slower than the P- wave, and consisting of a seismic vibration transverse to the direction of travel.
shear wave or transverse wave. Sometimes called converted waves because the particle motion is perpendicular to the direction of propagation. Shear waves are generated by the incidences of P-waves on surfaces at other than normal incidence.