bolus /bō″ləs/ [Gk, bolos, lump] , 1. a round mass, specifically a mass of solids and semisolids that have been chewed (masticated) and mixed with saliva during the oral preparation of swallow prior to being digested. Also called alimentary bolus. 2. a large round preparation of medicinal material for oral ingestion, usually soft and not prepackaged. 3. a dose of a medication or a contrast material, radioactive isotope, or other pharmaceutic preparation injected all at once intravenously. 4. (in radiotherapy) material used to fill in irregular body surfaces to improve dose distribution for hyperthermia or to increase the dose to the skin when high-energy photon beams are used. 5. a clumping in the stomach of ingested foreign material, often the result of habitual behavior.
