The Collaborative International Dictionary of English v.0.48:
Proof \Proof\, a.
1. Used in proving or testing; as, a proof load, or proof
2. Firm or successful in resisting; as, proof against harm;
I . . . have found thee
Proof against all temptation. --Milton.
This was a good, stout proof article of faith.
3. Being of a certain standard as to strength; -- said of
Proof charge (Firearms), a charge of powder and ball,
greater than the service charge, fired in an arm, as a gun
or cannon, to test its strength.
Proof impression. See under Impression.
Proof load (Engin.), the greatest load than can be applied
to a piece, as a beam, column, etc., without straining the
piece beyond the elastic limit.
Proof sheet. See Proof, n., 5.
Proof spirit (Chem.), a strong distilled liquor, or mixture
of alcohol and water, containing not less than a standard
amount of alcohol. In the United States "proof spirit is
defined by law to be that mixture of alcohol and water
which contains one half of its volume of alcohol, the
alcohol when at a temperature of 60[deg] Fahrenheit being
of specific gravity 0.7939 referred to water at its
maximum density as unity. Proof spirit has at 60[deg]
Fahrenheit a specific gravity of 0.93353, 100 parts by
volume of the same consisting of 50 parts of absolute
alcohol and 53.71 parts of water," the apparent excess of
water being due to contraction of the liquids on mixture.
In England proof spirit is defined by Act 58, George III.,
to be such as shall at a temperature of 51[deg] Fahrenheit
weigh exactly the 12/13 part of an equal measure of
distilled water. This contains 49.3 per cent by weight, or
57.09 by volume, of alcohol. Stronger spirits, as those of
about 60, 70, and 80 per cent of alcohol, are sometimes
called second, third, and fourth proof spirits
Proof staff, a straight-edge used by millers to test the
flatness of a stone.
Proof stick (Sugar Manuf.), a rod in the side of a vacuum
pan, for testing the consistency of the sirup.
Proof text, a passage of Scripture used to prove a