sinus

noun

si·​nus ˈsī-nəs 

: cavity, hollow: such as

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

Word History

Etymology

Middle English, from Medieval Latin, from Latin, curve, fold, hollow

First Known Use

15th century, in the meaning defined above

Phrases Containing sinus

• carotid sinus
• coronary sinus
• sinus node
• sinus rhythm
• sinus venosus
• urogenital sinus

Kids Definition

sinus

noun

si·​nus ˈsī-nəs 

: a hollow place : cavity

especially : any of several cavities in the skull that usually connect with the nostrils

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