Absolutely no meaning (at least to libertarians). According to Libertarians you can just disregard the phrase "general welfare" as if it were never written into the Constitution.
That is news to me. Would you care to substantiate that statement?
I take it to mean that 'particular welfare' (to individual people or corporations) is forbidden. But, I'm not on the Supreme Court. What, if anything, have they held it to mean? Is there any legislation that is authorised by it? or forbidden by it?