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
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
Despite these treatments, her health took a turn in May 2024 when a sinus infection spiraled into heart failure.
—Khloe Quill, FOXNews.com, 22 Aug. 2025
See All Example Sentences for sinus
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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
Despite these treatments, her health took a turn in May 2024 when a sinus infection spiraled into heart failure.
—Khloe Quill, FOXNews.com, 22 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 9 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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