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

Then came asthma, chronic sinus disease, and persistent cough. — Raja Flores, STAT, 11 Sep. 2026

Jamie Arnold, the A’s top pitching prospect, will also likely miss the rest of the season recovering from intra-orbital and maxillary sinus fractures suffered when he was hit by a line-drive to the left side of his face on Tuesday evening. — Johnny Flores Jr, New York Times, 9 Sep. 2026

The shiny brioche bun from Peter Sciortino Bakery squishes just right, hugging a healthy swipe of sinus-clearing horseradish mayo and a scattering of pickled onions underneath. — Rachel Bernhard, jsonline.com, 9 Sep. 2026

This is especially true for colds and other infections in the nose, throat and sinuses, many of which are caused by viruses and don’t need antibiotics at all. — Amy J. Mathers, The Conversation, 28 Aug. 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