In digestion, a bolus (from Latin bolus, ball) is a round mass of organic matter moving through the digestive tract. A bolus is initially shaped through chewing and swallowing of food and maintained as peristalsis moves it through the intestines.
The term "bolus" is also used in aerospace engineering to define the characteristics of human feces, when discussing devices for processing feces passed by a pilot while in space or air flight.
A radio-frequency identification tag ingested by livestock is also referred to as a bolus. It remains in the stomach of the animal for its lifetime and emits a unique ID that can be used to track an animal.