a
: a narrow elongated tract extending from a focus of suppuration and serving for the discharge of pus
b(1)
: a cavity in the substance of a bone of the skull that usually communicates with the nostrils and contains air
(2)
: a channel for venous blood
(3)
: a dilatation in a bodily canal or vessel
c
: a cleft or indentation between adjoining lobes (as of a leaf or corolla)
Cite this Entry
“Sinus.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/sinus. Accessed 14 Oct. 2026.
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