I offered her a sip-sip, the girl she gave me lip-lip
It did begin, the stuff wore in and now she's on my tip

from Beastie Boys – Brass Monkey Lyrics on Rap Genius


He attempts to get the girl to drink the cup, because it has the Spanish Fly in it. Eventually, it started to affect her and now she’s into him. “On my tip” implies she’s now having sex with him…

source: gotta-love-yauch

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