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

Busch was still at the top of his game when he was hit by his sinus infection. — Johnny Dodd, PEOPLE, 27 May 2026

An announcer calling that event said Busch had been suffering through a sinus cold all week. — Brian Niemietz, New York Daily News, 22 May 2026

Hospital staff initially diagnosed him with a sinus infection, gave him antibiotics, and sent him home. — Tiffani Jackson, Fort Worth Star-Telegram, 26 May 2026

Busch had been struggling with a sinus cold exacerbated by the intense G-forces and elevation changes at the New York road course, broadcasters said. — Mark Long, Chicago Tribune, 22 May 2026

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

Rhymes for sinus

• coyness
• dryness
• highness
• linus
• minus
• pinus
• shyness
• busyness
• equinus

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