D defs.my
Entry 2 senses Webster, 1913

Air sac

/ĕr săk/ · Air· sac · IPA
01 One of the spaces in different parts of the bodies of birds, which are filled with air and connected with the air passages of the lungs; an…
  1. 1.
    One of the spaces in different parts of the bodies of birds, which are filled with air and connected with the air passages of the lungs; an air cell.(Anat.)
  2. 2.
    An alveolus. See: alveolus