Definition of lung noun from the Oxford Advanced American Dictionary

Oxford3000

lung

noun
/lʌŋ/
 
 
either of the two organs in the chest that you use for breathing
lung cancer(humorous)She has a fine pair of lungs! (= she can sing or shout loudly)IDIOM

at the top of your voice/lungs

as loudly as possible
She was screaming at the top of her voice.at the top of your voiceat the top of your lungs