Synonyms and related words :
absolute, actual, admitting no question, certain, confirmable, demonstrable, demonstratable, factual, historical, impenetrable, impregnable, inappealable, incontrovertible, indisputable, indomitable, indubitable, inexpugnable, insuperable, invincible, inviolable, invulnerable, irrefragable, irrefutable, irresistible, overpowering, overwhelming, provable, real, resistless, self-evident, sure, testable, unanswerable, unassailable, unbeatable, unconfutable, unconquerable, uncontestable, undeniable, unimpeachable, unquestionable, unrefutable, unsubduable, unsurmountable, unyielding, verifiable