I. ˈprüf noun
Etymology: Middle English prof, prove, alteration of preve, from Anglo-French preove, from Late Latin proba, from Latin probare to prove — more at prove
Date: 13th century
1.
a. : the cogency of evidence that compels acceptance by the mind of a truth or a fact
b. : the process or an instance of establishing the validity of a statement especially by derivation from other statements in accordance with principles of reasoning
2. obsolete : experience
3. : something that induces certainty or establishes validity
4. archaic : the quality or state of having been tested or tried ; especially : unyielding hardness
5. : evidence operating to determine the finding or judgment of a tribunal
6.
a. plural proofs or proof : a copy (as of typeset text) made for examination or correction
b. : a test impression of an engraving, etching, or lithograph
c. : a coin that is struck from a highly polished die on a polished planchet, is not intended for circulation, and sometimes differs in metallic content from coins of identical design struck for circulation
d. : a test photographic print made from a negative
7. : a test applied to articles or substances to determine whether they are of standard or satisfactory quality
8.
a. : the minimum alcoholic strength of proof spirit
b. : strength with reference to the standard for proof spirit ; specifically : alcoholic strength indicated by a number that is twice the percent by volume of alcohol present
whiskey of 90 proof is 45 percent alcohol
II. adjective
Date: 1592
1. : able to resist or repel
boots that were… proof against cold and wet — Robertson Davies
— often used in combination
wind proof
2. : used in proving or testing or as a standard of comparison
3. : of standard strength or quality or alcoholic content
III. transitive verb
Date: 1745
1.
a. : to make or take a proof or test of
b. : proofread
2. : to give a resistant quality to
3. : to activate (yeast) by mixing with water and sometimes sugar or milk
• proof·er noun