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
When left untreated, this condition can lead to rare but potentially life-threatening complications, like cellulitis (a skin infection that can get into your bloodstream) and cavernous sinus thrombosis (a clot that restricts blood flow to your brain), Dr. Shokeen explains.
—
Jenna Ryu, SELF, 1 Nov. 2024
Because inhaling increases heart rate and exhaling decreases it, spending more time exhaling has the effect of gradually lowering your heart rate—this is known as respiratory sinus arrhythmia (RSA).
—Bryant Richardson, Forbes, 21 Oct. 2024
Simon died in Ojai, Calif. of sinus cancer while in hospice care, The New York Times reported.
—Rachel Desantis, Peoplemag, 13 Sep. 2024
Concerning causes of bradycardia include problems with the heart’s electrical signal, such as sick sinus syndrome.
—Carisa Brewster, Verywell Health, 12 Sep. 2024
See all Example Sentences for sinus 
Examples are automatically compiled from online sources to
show current usage.
Read More
Opinions expressed in the examples do not represent those of Merriam-Webster or its editors.
Send us feedback.
Jenna Ryu, SELF, 1 Nov. 2024
Because inhaling increases heart rate and exhaling decreases it, spending more time exhaling has the effect of gradually lowering your heart rate—this is known as respiratory sinus arrhythmia (RSA).
—Bryant Richardson, Forbes, 21 Oct. 2024
Simon died in Ojai, Calif. of sinus cancer while in hospice care, The New York Times reported.
—Rachel Desantis, Peoplemag, 13 Sep. 2024
Concerning causes of bradycardia include problems with the heart’s electrical signal, such as sick sinus syndrome.
—Carisa Brewster, Verywell Health, 12 Sep. 2024
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 22 Nov. 2024.
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
Love words? Need even more definitions?
Merriam-Webster unabridged
Share