1. (noun) a tiny sac for holding air in the lungs; formed by the terminal dilation of tiny air passageways

• air cell
• alveolus

1. (noun) a tiny sac for holding air in the lungs; formed by the terminal dilation of tiny air passageways

• sac

2. (noun) any of the thin-walled extensions of the tracheae of insects

• sac

3. (noun) any of the membranous air-filled extensions of the lungs of birds

• sac

1. (noun) a tiny sac for holding air in the lungs; formed by the terminal dilation of tiny air passageways

• alveolate
• cavitied
• faveolate
• honeycombed
• pitted