At what point should the prefix multi start to be used? See detail.

Ancient Rome.
MULTIBIBUS – drinks a lot
etc.

Two or more.

11 or more.

@rebbel No, I think that sounds too low.
@ragingloli That’s more like it according to when I hear it used. I never hear it being used before 10. In fact I hear it being used when it’s over 100 if it’s money.

“Multi” is a simple subjective plural designation, like “many”. There is no number.

@rebbel and @canidmajor are absolutely correct.

Multi just means more than one. For example, someone with $2 million is a multi-millionaire. It means more than one.

Just as if I had two girlfriends, I could be said to have multiple girlfriends.

I’ve changed my mind. Multi means more than one. It’s funny how we get in the wrong place because of usage. Even the dictionary (one of them which I posted in my OP anyway, I wonder if they all say that) says many or several

What dictionary was it?