The underground just spunned around and did a 360

from Eminem – Marshall Mathers Lyrics 1 on Rap Genius

“Underground” in rap has the same connotation as “indie” in rock (snobby, self-indulgent, sucks); the “underground” started out loving Eminem, but disowned him once Dre signed him

He says a 360(full-circle) rather than a 180(about-face) because when he was just starting out he was getting dissed for being white, etc., but he impressed the underground enough that they started to respect him… until he “went pop”.

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