If I gotta scream 'til I have half a lung
“Screaming out your lungs” is a hyperbolic idiom which means to scream really loudly. Eminem brilliantly flips the idiom. B. Rabbit is going to make you hear his voice no matter what it takes of him to do that. It can also be a metaphor for him getting so famous and ubiquitous that you can no longer avoid him or his music.
To help improve the meaning of these lyrics, visit “Rabbit Run” by Eminem Lyrics and leave a comment on the lyrics box