1. n. 
An elastic body wave in which particles oscillate perpendicular to the direction in which the wave propagates. S-waves are generated by most land seismic sources, but not by air guns. P-waves that impinge on an interface at non-normal incidence can produce S-waves, which in that case are known as converted waves. S-waves can likewise be converted to P-waves. S-waves, or shear waves, travel more slowly than P-waves and cannot travel through fluids because fluids do not support shear. Recording of S-waves requires receivers coupled to the solid Earth. Interpretation of S-waves can allow determination of rock properties such as fracture density and orientation, Poisson's ratio and rock type by crossplotting P-wave and S-wave velocities, and by other techniques.
See: acoustic, acoustic wave, body wave, converted wave, dilatancy theory, elastic, four-component seismic data, fracture, hodogram, P-wave, Poisson's ratio, seismic, SH-wave, shadow zone, shear, Snell's law, SV-wave, wave