the world > relative properties > quantity > greatness of quantity, amount, or degree > high or intense degree > [adverb] > extremely or exceedingly > incredibly (4)
In an incredible manner or degree, in a way or to an extent that is impossible or very difficult to believe; to an extent that one would not have…
as adv. = incredibly, adv. Obsolete.
In an inconceivable manner or degree. Often exaggerative for ‘extraordinarily’, ‘extremely’, ‘very highly’.