柯林斯词典air sac 1. N any of the membranous air-filled extensions of the lungs of birds, which increase the efficiency of gaseous exchange in the lungs (鸟类的)气囊 返回 air sac剑桥词典a space filled with air that continues from a bird's lungs into one of its bones or another body area , used in breathing 气囊（鸟类体内从肺部延伸至骨骼以及其他身体部分的气囊，用于呼吸） a wide part like a bag in the tubes an insect uses for breathing （昆虫的）气囊 an alveolus (= a very small air bag in the lungs ) 肺泡 返回 air sac