-proof

Collins Concise English Dictionary © HarperCollins Publishers::

-proof combining_form

1. secure against (damage by); (make) impervious to: waterproof, mothproof, childproof

Etymology: from proof (adj)

WordReference Random House Learner's Dictionary of American English © 2026

proof /pruf/   n. 

1. [uncountable] evidence or facts that are sufficient to establish a thing as true or believable.
2. Mathematics, Philosophy [countable] a sequence of steps, statements, or demonstrations that leads to and establishes a valid conclusion.
3. Wine [uncountable] the strength of an alcoholic liquor, esp. with reference to the standard whereby 100 proof signifies an alcoholic content of 50 percent.
4. Photography [countable] a print made from a negative of a photograph for checking quality.
5. Printing [countable] a preliminary copy, as of a manuscript, that is printed for correction or changes.

adj. [be + ~]

6. able to withstand or resist something harmful or undesirable:
   a shelter that was proof against the cold.

v. [~ + object]

7. to proofread:
   Proof the document.See -prov-.

-proof, suffix. 

1. -proof is used to form adjectives with the meaning "resistant;
   not allowing through'' the word mentioned:
   child + -proof → childproof (= resistant to a child opening it);
   water + proof → waterproof (= not allowing water through).

WordReference Random House Unabridged Dictionary of American English © 2026

proof  (pro̅o̅f ), n. 

1. evidence sufficient to establish a thing as true, or to produce belief in its truth.
2. anything serving as such evidence:
   What proof do you have?
3. the act of testing or making trial of anything;
   test;
   trial:
   to put a thing to the proof.
4. the establishment of the truth of anything;
   demonstration.
5. Law (in judicial proceedings) evidence having probative weight.
6. the effect of evidence in convincing the mind.
7. Mathematics an arithmetical operation serving to check the correctness of a calculation.
8. Mathematics, Philosophy a sequence of steps, statements, or demonstrations that leads to a valid conclusion.
9. a test to determine the quality, durability, etc., of materials used in manufacture.
10. Wine [Distilling.]
    • the arbitrary standard strength, as of an alcoholic liquor.
    • strength with reference to this standard: "100 proof '' signifies a proof spirit, usually 50% alcohol.
11. Photography a trial print from a negative.
12. [Print.]
    • Printing a trial impression, as of composed type, taken to correct errors and make alterations.
    • Printing one of a number of early and superior impressions taken before the printing of the ordinary issue:
      to pull a proof.
13. Printing (in printmaking) an impression taken from a plate or the like to show the quality or condition of work during the process of execution;
    a print pulled for examination while working on a plate, block, stone, etc.
14. Currency [Numis.] one of a limited number of coins of a new issue struck from polished dies on a blank having a polished or matte surface.
15. the state of having been tested and approved.
16. proved strength, as of armor.
17. Scottish Terms the trial of a case by a judge alone, without a jury.

adj. 

18. able to withstand;
    successful in not being overcome:
    proof against temptation.
19. impenetrable, impervious, or invulnerable:
    proof against outside temperature changes.
20. used for testing or proving;
    serving as proof.
21. of standard strength, as an alcoholic liquor.
22. of tested or proven strength or quality:
    proof armor.
23. noting pieces of pure gold and silver that the U.S. assay and mint offices use as standards.

v.t. 

24. to test;
    examine for flaws, errors, etc.;
    check against a standard or standards.
25. Printing prove (def. 7).
26. to proofread.
27. to treat or coat for the purpose of rendering resistant to deterioration, damage, etc. (often used in combination):
    to proof a house against termites; to shrink-proof a shirt.
28. Food [Cookery.]
    • to test the effectiveness of (yeast), as by combining with warm water so that a bubbling action occurs.
    • to cause (esp. bread dough) to rise due to the addition of baker's yeast or other leavening.

• Late Latin proba a test, akin to Latin probāre to test and find good; compare pree
• Middle French preve, proeve, prueve
• Middle English prove, prooff, prof, proufe, alteration (by association with the vowel of prove) of preove, proeve, prieve, pref 1175–1225

Synonyms

• 1. confirmation, demonstration, corroboration, support. See evidence. 
• 3. examination, assay.
• 18. firm, steadfast.

-proof, 

1. a combining form meaning "resistant, impervious to'' that specified by the initial element:
   burglarproof;
   childproof;
   waterproof.