Used as an adjective and sometimes as a noun, it refers to something stern, harsh, unyielding, inflexible, rigid, sturdy, strong, robust.
en.wikipedia.org The lyrics are rather ambiguous, sung and screamed with an urgency that complements the unyielding compositions.
en.wikipedia.org The governor was unyielding to their defiance but a mob retrieved the seized ships.
en.wikipedia.org Described as having been a frivolous and high-spirited princess, she also, at an early age, had displayed a tendency to be both stubborn and unyielding.
en.wikipedia.org It is not merely about passive endurance, but an act of unyielding resistance and defiance.
en.wikipedia.org