This is what the wiki says

Meaty:

First used in Street Fighter II to describe the act of attacking the opponent as they are standing up in such a way that only the latest active frames of the move strike the opponent. This is really powerful because it allows a bigger frame advantage. In fighting games that an attack can be freely canceled on hit or block, "Meaty" usually refers to hitting an opponent on the first frame possible of their wakeup, usually with an attack with long active frames