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

For a while, Vette experienced lingering sinus issues, which doctors initially brushed off as an infection. —Okla Jones, Essence, 30 Jan. 2026

His brand, Wizard Wellness, launches Thursday on its website with sinus rinses, nasal sprays, nasal sticks and oral strips, plus bundles around routines with each. —James Manso, Footwear News, 29 Jan. 2026

Available in 18-count, 24-count and 36-count bottles, this medicine provides maximum strength to clear sinus congestion and pressure. —Bestreviews, Chicago Tribune, 23 Jan. 2026

Your tropical plants and your sinuses will thank you. —Leanne Potts, Better Homes & Gardens, 21 Jan. 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