refusing to give in

unyielding

having or showing a great deal of confidence

aggressive

decisive; critical

critical, important

theoretical (and not thinking about practical problems)

dogmatic, opinionated

determined and stubborn when trying to solve or complete something

determined, persistent

urgent; essential

necessary

that cannot be satisfied

voracious, wanting

coming or happening at once; urgent; (of food, drink) that can be prepared quickly and easily

immediate, urgent

urgent; requiring immediate attention

important; urgent

important and so needing a quick decision or action; (of a person, voice etc) showing that something is urgent

needing immediate attention