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)
Examples of sinus in a Sentence
Recent Examples on the Web
Pneumococcal disease is a bacterial infection that can cause many different illnesses, including pneumonia, blood infections, meningitis, and ear and sinus infections.
—
Michelle Marchante
september 8, Miami Herald, 8 Sep. 2025
Despite a rough sinus infection, George Clooney put on a brave face to be at the red carpet world premiere of his new movie, Jay Kelly, in Venice last night.
—Andreas Wiseman, Deadline, 29 Aug. 2025
The fatal case in Missouri follows the deaths of a 12-year-old boy who got sick after swimming in a South Carolina lake and a 71-year-old woman in Texas who contracted the infection by using tap water to clear out her sinuses.
—N'dea Yancey-Bragg, USA Today, 28 Aug. 2025
The actor also cut short some media commitments the day prior — and reportedly bailed on a swanky private dinner held with his director, Noah Baumbach, and fellow castmembers — due to a bad sinus infection.
—Patrick Brzeski, HollywoodReporter, 28 Aug. 2025
See All Example Sentences for sinus
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Michelle Marchante
september 8, Miami Herald, 8 Sep. 2025
Despite a rough sinus infection, George Clooney put on a brave face to be at the red carpet world premiere of his new movie, Jay Kelly, in Venice last night.
—Andreas Wiseman, Deadline, 29 Aug. 2025
The fatal case in Missouri follows the deaths of a 12-year-old boy who got sick after swimming in a South Carolina lake and a 71-year-old woman in Texas who contracted the infection by using tap water to clear out her sinuses.
—N'dea Yancey-Bragg, USA Today, 28 Aug. 2025
The actor also cut short some media commitments the day prior — and reportedly bailed on a swanky private dinner held with his director, Noah Baumbach, and fellow castmembers — due to a bad sinus infection.
—Patrick Brzeski, HollywoodReporter, 28 Aug. 2025
See All Example Sentences for sinus
Cite this Entry
“Sinus.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/sinus. Accessed 16 Sep. 2025.
Copy CitationKids Definition
Medical Definition
sinus
noun
si·nus
ˈsī-nəs 
: a cavity or hollow in the body: as
a
: a narrow elongated tract extending from a focus of suppuration and serving for the discharge of pus
a tuberculous sinus
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
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