Merriam-Webster Logo
SINCE 1828
Menu
×

An Encyclopædia Britannica Company

See What's Trending Now See More Trending Words

air sac

noun

Definition of air sac

1 :one of the air-filled spaces in the body of a bird connected with the air passages of the lungs
2 :alveolus 1b
3 :a thin-walled dilation of a trachea occurring in many insects

See air sac defined for kids

Explore M-W

alt-59e673567065d
The History of the Word 'Terrorism'
knupfer-painting-solon-before-croesus
Forms of Government Quiz
video-title-words-of-the-year-1066
Words of the Year: 1066
alt-59e60c9d3e5ea
Trending: McCain: Half-Baked, 'Spurious' Nationalism

First Known Use of air sac

circa 1805

AIR SAC Defined for Kids

air sac

noun

Definition of air sac for Students

:one of the small pouches in the lungs where oxygen and carbon dioxide are exchanged

Medical Dictionary

air sac

noun

medical Definition of air sac

:alveolus b

Learn More about air sac

  1. Britannica.com: Encyclopedia article about air sac

Seen and Heard

What made you want to look up air sac? Please tell us where you read or heard it (including the quote, if possible).

show hide

Love words? Need even more definitions?

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!

WORD OF THE DAY

euphony

play

pleasing or sweet sound

Get Word of the Day daily email!

TRENDING NOW

  1. spurious of a deceitful nature or quality

  2. righteous We provide an assortment of definitions

  3. Kafkaesque 'A nightmarish quality'

  4. mike "microphone"

  5. moron “a very stupid person”

SEE ALL

BROWSE DICTIONARY

air sac

Test Your Vocabulary

Forms of Government Quiz

  • knupfer-painting-solon-before-croesus
  • A gerontocracy is rule by:
How Strong Is Your Vocabulary?

Test your vocabulary with our 10-question quiz!

TAKE THE QUIZ
Word Winder's CrossWinder

Test Your Knowledge - and learn some interesting things along the way.

TAKE THE QUIZ

Love words? Need even more definitions?

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!

Words at Play

alt-59e673567065d
The History of the Word 'Terrorism'

Noah Webster first entered the term in 1840

alt-59e65152518a6
'Regimen' vs. 'Regiment'

The rule of thumb for words about rules

alt-59e50f5a357b4
'Spox' May Go On The Record

From newsroom lingo to the mainstream

alt-59e506c5c02ae
C'mon, Of Course 'Myriad' Is a Noun

For a myriad of reasons

Ask the Editors

video-title-words-of-the-year-1066
Words of the Year: 1066

Or, Why Pig Meat is Called 'Pork' and Cow Meat is Called 'Beef'

payday
How Often Is 'Biweekly'?

Don't get us started on 'bimonthly'

video-irregardless-grammar-peeve-blend-of-the-synonyms-irrespective-and-regardless
Irregardless

It is in fact a real word (but that doesn't mean you should use it).

video-moose-goose-weird-plurals
Weird Plurals

One goose, two geese. One moose, two... moose. What's up with that?

Word Games

knupfer-painting-solon-before-croesus
Forms of Government Quiz

Name that government! Or something like that.

Take the quiz
rembrandt-painting-a-young-scholar-and-his-tutor
Original Meanings Quiz

A quiz for the pedantic and those annoyed by them!

Take the quiz
How Strong Is Your Vocabulary?
How Strong Is Your Vocabulary?

Test your vocabulary with our 10-question quiz!

Take the quiz
Word Winder's CrossWinder
Word Winder's CrossWinder

A game of winding words.

Play the game