Reprobate - Vine's Expository Dictionary of New Testament Words
Reprobate[ 1,,G96, adokimos ]
signifying not standing the test, rejected" (a, negative, dokimos, "approved"), was primarily applied to metals (cp. Isaiah 1:22); it is used always in the NT in a Passive sense,
(a) of things, Hebrews 6:8, "rejected," of land that bears thorns and thistles;
(b) of persons, Romans 1:28, of a "reprobate mind," a mind of which God cannot approve, and which must be rejected by Him, the effect of refusing "to have God in their knowledge;" in 1 Corinthians 9:27 (for which See CAST, REJECTED); 2 Corinthians 13:5-7, where the RV rightly translates the adjective "reprobate" (AV, "reprobates"), here the reference is to the great test as to whether Christ is in a person; in 2 Timothy 3:8 of those "reprobate concerning the faith," i.e., men whose moral sense is perverted and whose minds are beclouded with their own speculations; in Titus 1:16, of the defiled, who are "unto every good work reprobate," i.e., if they are put to the test in regard to any good work (in contrast to their profession), they can only be rejected. In the Sept., Proverbs 25:4; Isaiah 1:22.