1. A diagnostic procedure designed to determine the density of a body part by the sound produced by tapping the surface with the finger or a plessor; performed primarily over the chest to determine presence of normal air content in the lungs and over the abdomen to evaluate air in the loops of intestine and the size of solid organs such as the liver and spleen.
2. A form of massage, consisting of repeated blows or taps of varying force.
The definition information for percussion is provided by Stedman's. You can search our medical dictionary here.