Yes, when we talk about "y'all" it typically refers to a group of three or more individuals.
"Y'all" is a contraction of "you all" and is commonly used in Southern American English as a plural form of "you." In this context, "mean" is not clear. If you are asking whether "y'all" means three organisms, the answer is no. "Y'all" simply refers to a group of people, and has no connection to organisms.
I'm sorry, but I'm not sure I understand your question. Could you please provide more context or clarify what you mean by "yall mean 3 organisms right"?
