Such were ‘Ad (people). They rejected the Ayat (proofs, evidences, verses, lessons, signs, revelations, etc.) of their Lord and disobeyed His Messengers, and followed the command of every proud obstinate (oppressor of the truth, from their leaders).
Meaning:-
Obstinate: stubbornly refusing to change one’s opinion or chosen course of action, despite attempts to persuade one to do so.