When someone is so fat that it's hard to penetrate their ass/pussy, they are known as "solid butter" because they're too thick to spread.
Person 1: Ayy man I heard you fucked that fat chick last night. How was she?

Person 2: She was no good. That bitch was a solid butter.

Person 1: You mean she's fat from eating lots of butter?

Person 2: No, she's a solid butter because she's too thick to spread.
by JustEnough June 5, 2023
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