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
Dry air can irritate the sinuses and make a cough worse.
—
Emily Dashiell, Verywell Health, 12 Dec. 2024
In the short term, wildfire smoke can cause sore throats, wheezing, and irritation to the eyes, sinuses, and skin, which can be managed with remedies like sinus rinses and moisturizers.
—Amanda Castro, Newsweek, 14 Jan. 2025
Mucus is a substance that lines the moist surfaces of your body, including the lungs, sinuses, mouth, stomach, intestines, and eyes.
—Korin Miller, Health, 18 Dec. 2024
Here’s how to care for your eyes, sinuses and skin during a wildfire
Jan. 10, 2025
On Sunday Zula Den, a nonprofit wellness center on Jefferson Boulevard, held a free wellness day that included acupuncture, massage, sound baths and reiki.
—Deborah Vankin, Los Angeles Times, 15 Jan. 2025
See all Example Sentences for sinus 
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Emily Dashiell, Verywell Health, 12 Dec. 2024
In the short term, wildfire smoke can cause sore throats, wheezing, and irritation to the eyes, sinuses, and skin, which can be managed with remedies like sinus rinses and moisturizers.
—Amanda Castro, Newsweek, 14 Jan. 2025
Mucus is a substance that lines the moist surfaces of your body, including the lungs, sinuses, mouth, stomach, intestines, and eyes.
—Korin Miller, Health, 18 Dec. 2024
Here’s how to care for your eyes, sinuses and skin during a wildfire
Jan. 10, 2025
On Sunday Zula Den, a nonprofit wellness center on Jefferson Boulevard, held a free wellness day that included acupuncture, massage, sound baths and reiki.
—Deborah Vankin, Los Angeles Times, 15 Jan. 2025
See all Example Sentences for sinus
Dictionary Entries Near sinus
Cite this Entry
“Sinus.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/sinus. Accessed 21 Feb. 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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