noun Date: circa 1828 one of the air-filled spaces in the body of a bird connected with the air passages of the lungs, alveolus 1b, a thin-walled dilation of a trachea occurring in many insects
AIR SAC
Meaning of AIR SAC in English
Merriam Webster. Explanatory English dictionary Merriam Webster. Толковый словарь английского языка Мерриам-Уэбстер. 2012