air sac

noun

1

: one of the air-filled spaces in the body of a bird connected with the air passages of the lungs

2

: alveolus sense 1b

3

: a thin-walled dilation of a trachea occurring in many insects

Examples of air sac in a Sentence

Recent Examples on the Web

Adenocarcinoma — which starts in the cells lining the air sacs in the lungs — is the most common type of lung cancer among people who have never smoked, comprising up to 50% of diagnoses in that group, per the Centers for Disease Control and Prevention (CDC). —Melissa Rudy, Fox News, 18 Feb. 2025

Paleontologists have proposed that air sacs emanating from the respiratory systems of many dinosaurs surrounded and invaded their bones, which allowed their skeletons to be lighter without sacrificing strength, with the bonus of helping the animals breathe more efficiently. —Riley Black, Smithsonian Magazine, 6 May 2025

Birds today have hollow bones, which give space for soft tissue air sacs that are connected to the lungs. —Joshua Rapp Learn, Discover Magazine, 19 Apr. 2025

Regrowing Teeth Is on the Horizon and May Represent the Future of Dentistry Poor Oral Health and Other Chronic Diseases The mouth is also linked to other chronic diseases, such as respiratory infections like pneumonia and infections of the air sacs in the lungs. —Sara Novak, Discover Magazine, 14 Mar. 2025

Word History

First Known Use

circa 1805, in the meaning defined at sense 1

Rhymes for air sac

• aback
• anzac
• attack
• backpack
• backtrack
• bareback
• blackjack
• brownback
• buyback
• callback
• cognac
• comeback

Kids Definition

air sac

noun

1

: one of the air-filled spaces connected with the lungs of a bird

2

: one of the thin-walled microscopic pouches in which gases are exchanged in the lungs

Medical Definition

air sac

noun

: alveolus sense b