It's not the appeals court's job to "define what AI means," their job is to rule on the case in front of them. This particular case involved someone asserting copyright over an image that he claimed was generated by a sentient[0] AI. This image was not created by a human, and only works created by humans can be copyrighted under US law, so they ruled against him.

[0]https://thenewstack.io/stephen-thaler-claims-hes-built-a-sen...