1. The rippling motion of muscles in the digestive tract: In the stomach, this peristalsis or movement mixes food with gastric juices, turning them into a thin liquid.
2. The activity by which the alimentary canal and other tubular organs, that have both longitudinal and circular muscle fibers, propel their contents: The peristalsis consists of a wave of contractions passing along the tube for variable distances.
3. The wormlike motions by which the stomach and the bowels propel or send their contents: Peristalses consist of alternate waves of relaxations and contractions in successive parts of the intestinal tube and any obstructions to the flow of the contents will cause these contractions to become stronger and are often accompanied by a severe form of pain known as "colic" or an attack of spasmodic pain in the abdomen.

Food and digestion products are pushed through the intestine from the throat to the rectum, by peristalsis or the surging of muscular contractions of the intestinal wall.

4. Etymology: from Greek peri, "around" + stalsis, "contraction".

Forced movements of short duration in which the contents of the colon are moved from one section to another area: Mass peristalsis takes place three or four times each day.

Movement in the opposite direction to that which is normal: Reverse peristalsis consists of an intestinal squeezing that goes in a direction that is the opposite of what generally takes place during which the contents of the intestine are forced backward.