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

According to the National Audubon Society, male sage grouse perform courtship displays — fanning their tails, inflating air sacs and producing popping sounds to attract females. —Samantha Agate, Kansas City Star, 14 Apr. 2026

According to the National Audubon Society, male sage grouse perform courtship displays on communal breeding grounds called leks — fanning their tails, inflating air sacs and producing popping sounds to attract females. —Samantha Agate, Fort Worth Star-Telegram, 14 Apr. 2026

Males fan their tails, inflate air sacs and produce popping sounds to attract females, according to the National Audubon Society. —Samantha Agate, Miami Herald, 14 Apr. 2026

For now, though, Snelling doesn’t expect air sacs to suddenly cause a miraculous comeback of the oxygen-constraint hypothesis. —Jacek Krywko, ArsTechnica, 28 Mar. 2026

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