marked by firm determination or resolution; not shakable; firm convictions; a firm mouth; steadfast resolve; a man of unbendable perseverence; unwavering loyalty

[ Syn: firm , steadfast , steady , stiff , unbendable , unfaltering , unwavering ]

without flaws or loopholes; an ironclad contract; a watertight alibi; a bulletproof argument

[ Syn: unassailable , watertight , bulletproof ]