Unlimited in this context means unstoppable, "motherfucker" names the object of the sentence, note that it is not meant to be offensive, or used to antagonize. "Motherfucker unlimited" is most frequently used as a compliment.
"Kendra did a back flip off a pick up truck, and immediately did a keg stand... Wtf..."

"Holy shit what, mother fucker unlimited!"

"Wait what does motherfucker unlimited mean?"

"Uhhh... Like she's cool? Unstoppable? Idk man, just feels good to say"
by Lemonsugar420 September 14, 2020
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