Meat is defined as the flesh of animals
Yes, and cultured meat is unquestionably the flesh of animals. It's grown directly from real animal cells, real animal DNA, etc. Therefore, obviously, it's meat. Trying to say it isn't is either a demonstration of a complete ignorance of the science, or disingenuous nonsense unworthy of the claimant or those the claims are being made to.
The USDA's definition doesn't say "has to be from a slaughtered animal carcass."
Fully hyphenated would be better, "Lab-Grown-Meat" or perhaps "Cultured-Meat".
Sure, seems fine. Might want to call the other stuff "Slaughtered-Meat", too. Just so everyone's clear.
Related, I 100% object to calling plant-based products "meat." They aren't meat by any reasonable definition. Calling them meat is outright deceptive. Being a curmudgeonly crank, whenever it comes up in conversation, I say, "Oh... you mean salad. :)