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

While most infections occur during recreational freshwater activities, people trying to clean their sinuses are advised to use distilled, sterilized or boiled — and then cooled — water to avoid infection or illness. —David Matthews, New York Daily News, 6 June 2025

The dura can be damaged from head injuries or punctured during surgical procedures involving the sinuses, brain or spine, such as lumbar puncture, epidurals, spinal anesthesia or myelogram. —Danielle Wilhour, The Conversation, 28 May 2025

One chemical included hexavalent chromium, a carcinogen that can lead to nasal and sinus cancers, kidney and liver damage, nasal and skin irritation and ulceration, and eye irritation and damage, according to the National Institute of Environmental Health Sciences. —Maya Wilkins, Chicago Tribune, 28 May 2025

Research suggests that bromelain has anti-inflammatory properties and helps ease sore throats and clear sinuses. —Julie Marks, Verywell Health, 19 May 2025

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