S wave n.
A downward deflection of the QRS complex in an electrocardiogram following an R wave.
A type of seismic body wave in which rock particles vibrate at right angles to the direction of wave travel. Secondary waves cause the rocks they pass through to change in shape. These waves are the second fastest traveling seismic waves (after primary waves) and can travel through solids but not through liquids or gases. Also called shear wave, S wave. See Note at earthquake.