Synonyms of the word

bulletproof

• adj. (of a material) Capable of withstanding a direct shot by a bullet fired from a gun.
• adj. (idiomatic) reliable, infallible, sturdy or error-tolerant.
• adj. (usually of an idea or concept) Unbreakable, very tough.
• v. To make proof against bullets.
• v. (slang) to make resistant to failure.

armored

• adj. Clad or equipped with arms or armor.
• adj. Covered with armor, as a ship or the face of a fortification; armor-plated.
• v. simple past tense and past participle of armor.

armoured

• adj. Possessing, wearing, or fitted out with armour.
• adj. (military) Equipped with armoured vehicles.
• v. simple past tense and past participle of armour.

incontestable

• adj. Not contestable; indisputable; certain; incontrovertible.

incontestible

• adj. Alternative spelling of incontestable.

proof

• n. (countable) An effort, process, or operation designed to establish or discover a fact or truth; an act…
• n. (uncountable) The degree of evidence which convinces the mind of any truth or fact, and produces belief;…
• n. The quality or state of having been proved or tried; firmness or hardness which resists impression, or…
• n. (obsolete) Experience of something.
• n. (uncountable, obsolete) Firmness of mind; stability not to be shaken.
• n. (countable, printing) A proof sheet; a trial impression, as from type, taken for correction or examination.
• n. (countable, logic, mathematics) A sequence of statements consisting of axioms, assumptions, statements…
• n. (countable, mathematics) A process for testing the accuracy of an operation performed. Compare prove,…
• n. (obsolete) Armour of excellent or tried quality, and deemed impenetrable; properly, armour of proof.
• n. (US) A measure of the alcohol content of liquor. Originally, in Britain, 100 proof was defined as 57.1%…
• adj. Used in proving or testing.
• adj. Firm or successful in resisting.
• adj. (of alcoholic liquors) Being of a certain standard as to alcohol content.
• v. (transitive, intransitive, colloquial) To proofread.
• v. (transitive) To make resistant, especially to water.
• v. (transitive, cooking) To allow to rise (of yeast-containing dough).
• v. (transitive, cooking) To test the activeness of (yeast).

unassailable

• adj. secure against attack; impregnable.
• adj. (by extension) undeniable, incontestable or incontrovertible.

unshakable

• adj. Not able to be shaken; firm, solid.
• adj. resolute, unfaltering, unwavering.
• adj. (figuratively) Having no errors or loopholes; unassailable.

watertight

• adj. So tightly made that water cannot enter or escape.
• adj. So devised or planned as to be impossible to defeat, evade or nullify.