What is the definition or description of: peristalsis?

See below: Peristalsis is a series of organized muscle contractions that occur throughout the digestive tract. Peristalsis is also seen in the tubular organs that connect the kidneys to the bladder. Peristalsis is an automatic and important process that moves food through the digestive system. It also moves urine from the kidneys into the bladder, and bile from the gallbladder into the duodenum.