Turned the bathroom into a smashroom
She was hitting lines he was hitting from behind

from Killer Mike – JoJo's Chillin' Lyrics on Rap Genius

Meaning

Turning the bathroom into a “smash room” is fairly self evident, a smash room being where things get smashed. The fact that she’s hitting lines (doing coke) while getting ‘smashed’ makes her a genuine party girl.

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