She just, she just, she just, she just want a long dick
I put it in her mouth and now that bitch look like a conehead

from Big Sean – What U Doin? (Bullshitting) Lyrics on Rap Genius

A use of imagery here. If one has a long ‘dick’, per-se, if heads were made of rubber like flexible substances, then when a woman is giving oral sex, the dick will stretch the head and make it into a cone shape.

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