| Sustainable (a.) Capable of being sustained or maintained; as, the action is not sustainable. Thesaurus Entries absolute, actual, admitting no question, apodictic, apparent, attestable, authenticatable, certain, checkable, conclusive, confirmable, demonstratable, demonstrated, displayable, displayed, evident, evincible, exhibitable, exhibited, factual, historical, inappealable, incontestable, incontrovertible, indisputable, indubitable, irrefragable, irrefutable, manifest, obvious, positive, provable, real, self-evident, shown, substantiatable, supportable, sustainable, testable, unanswerable, unconfutable, undeniable, unimpeachable, unquestionable, unrefutable, validatable, verifiable | ![]() |