What does bolus mean?
A bolus is a discrete mass of something — most familiarly, the ball of chewed food that the tongue pushes back and swallows in a single motion. The word belongs mainly to technical registers. Physiologists use it to describe how food travels through the esophagus, while clinicians use it in a second sense: a concentrated dose of medication delivered all at once rather than gradually, such as an intravenous bolus of fluids or an insulin bolus timed to a meal. Veterinary medicine uses the term for large, oblong pills designed for livestock, which lodge in the animal's rumen and release nutrients slowly. Borrowed from ancient Greek, where it meant simply a lump, the word carries a precise, clinical connotation today. It is worth knowing because it appears constantly in medical writing and diabetes management, where patients themselves routinely speak of programming boluses — making this once-obscure Greek lump part of everyday healthcare vocabulary.
nounA single mass of a substance, especially the rounded mass of chewed food that is swallowed at once, or in medicine a concentrated dose of a drug given rapidly into the bloodstream.
- A rounded mass of chewed food ready to be swallowed.
- In medicine, a single concentrated dose of a drug (such as insulin) administered at one time, often intravenously.
- In veterinary medicine, an oblong pill or large pill-shaped mass given orally to livestock.
"The radiologist watched the bolus of barium move down the patient's esophagus on the monitor."
"Diabetics on an insulin pump can program a bolus to cover the carbohydrates in a meal."
"The farmer administered a mineral bolus to the herd as part of its routine care."
Both plurals are standard; "boluses" follows regular English formation, while "boli" reflects the word's Latin-like ending and is favored in some medical contexts.
"The protocol calls for two boluses of saline during the procedure."
Every bite you swallow has a scientific name before it even reaches your stomach — it's a bolus, and your digestive tract treats each one as a carefully packaged parcel.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of bolus
The English word "bolus" comes directly from the ancient Greek "bōlos," meaning a lump or clod of earth. It entered English via Latin in the early modern period, first appearing in medical contexts describing masses of food or medicine. The Greek term itself is of uncertain deeper origin, so while "bolus" is firmly rooted in Greek, few common English words are true siblings sharing the same root.
How bolus is actually used
Primarily a technical term used in medicine, dentistry, physiology, and veterinary practice; rarely heard in casual conversation. In clinical settings "bolus" almost always refers to drug administration, while in anatomy and physiology it refers to the mass of chewed food.
Easily confused with bolus
"Boules" refers to a French lawn game played with metal balls, while "bolus" denotes a mass of chewed food or a medical dose; they look similar but share nothing else.