inexpugnable

having been established and usually not subject to change an inexpugnable belief in the essential goodness of people Synonyms certain, determinate, final, firm, flat, frozen, hard, hard-and-fast, fixed, set, settled, stableRelated Words nonadjustable, noncancelable, nonnegotiable, unchangeable; constant, steady, unchanging, uniform, unwavering; definite, exact, explicit, specific; given, stated, stipulated; dependable, good, reliable, responsible, safe, solid, sure, tried, tried-and-true, true, trustworthy, trustyNear Antonyms adjustable, changeable, negotiable; indefinite, open-ended, unspecified; capricious, changeful, flickery, fluctuating, fluid, inconstant, mercurial, mutable, temperamental, uncertain, unpredictable, unsettled, unstable, unsteady, variable, volatile