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Concise Oxford English Dictionary
bolus
‘bəʊləs
■ noun (plural boluses)
a small rounded mass of a substance, especially of food being swallowed.
a large pill used in veterinary medicine. ▶Medicine a single dose of a drug given all at once.

C16: via late L. from Gk bōlos ‘clod’.
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Merriam-Webster Collegiate® Dictionary
bo·lus
Pronunciation: ‘bō-ləs
Function: noun
Inflected Form: plural bo·lus·es
Etymology: Late Latin, from Greek bōlos lump
Date: 1562

1 : a rounded mass: as a : a large pill b : a soft mass of chewed food
2 : a dose of a substance (as a drug) given intravenously specifically : a large dose given for the purpose of rapidly achieving the needed therapeutic concentration in the bloodstream