Jagged means you've gone to an extremely low body fat percentage where the striations or lines within your glutes have become visible to the naked eye. Only when lines are visible to the naked eye can one claim to be jagged.
* These videos are coming directly from Youtube, they may or may not be most relevant to the word "Jagged"
What is Define Dictionary Meaning?
Best thing is, its free and you can even contribute without creating an account.