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

Unfortunately, pneumonia, an infection that causes inflammation in the air sacs of the lungs and fills them with pus or fluid, causes 1.2 million emergency room visits and 41,000 deaths per year, according to data from the Centers for Disease Control and Prevention (CDC). —Helen Carefoot, Flow Space, 20 Oct. 2025

In severe cases, RSV can lead to pneumonia, which occurs when the air sacs in the lungs become swollen and filled with fluid or pus. —Liz Szabo, Scientific American, 23 Sep. 2025

This inflammation leads to extensive damage, causing fluid to leak from other parts of the lung into the air sacs. —Katherine Weaver, Chicago Tribune, 28 Aug. 2025

Accounts Samsung Confirms Upgrade Choice—Galaxy Users Must Now Decide In the spring, males would gather in leks and perform dramatic dances, puffing out orange air sacs on their necks and stomping their feet to show dominance and vitality. —Scott Travers, Forbes.com, 8 June 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