abiding accordant adamant adamantine alike automatic balanced cast-iron changeless consistent consonant constant continuing continuous correspondent dour durable enduring equable equal even firm fixed flat flinty frozen grim hard hard-core homogeneous immobile immovable immutable implacable impliable inalterable incommutable inconvertible indefeasible inelastic inert inexorable inflexible insusceptible of change intact intransigent intransmutable invariable inviolate iron irreconcilable irretrievable irreversible irrevocable lasting level measured mechanical methodic monolithic noble nonreturnable nonreversible of a piece ordered orderly permanent perpetual persistent quiescent regular relentless remaining reverseless rigid rigorous robotlike rock-ribbed smooth solid stable static stationary staying steadfast steady steely stern stiff sustained systematic torpid unaffected unalterable unalterative unaltered unbending unbroken unchanged unchanging unchecked uncompromising undeflectable undestroyed undeviating undifferentiated undiversified unfading unfailing ungiving uniform unmodifiable unmovable unmoved unrelenting unremitting unrestorable unreturnable unruffled unshifting unsusceptible unvariable unvaried unvarying unyielding