1. n. 
Also known as S-wave, 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.