I am looking for a word to describe a word or a sentence that is hard to pronounce, in a situation that even you know the pronunciation but just can't control your tongue. Tongue-twister is the closest that I have come up with so far, but I wonder if there is an adjective.
I want a word that can fit into the blanks:
The script was so _________ that I had to pause and repeat a lot.
This rap is insanely ________.(a word more specific than "hard"/"difficult")