Thayer's Greek LexiconSTRONGS NT 114: ἀθετέω
ἀθετέω, (ῶ; future ἀθετήσω; 1 aorist ἠθέτησα; a word met with first (yet very often) in the Sept. and Polybius;
a. properly, to render ἄθετον; do away with θετόν τί, i. e. something laid down, prescribed, established: διαθήκην, Galatians 3:15 (1 Macc. 11:36; 2 Macc. 13:25, etc.); according to the context, 'to act toward anything as though it were annulled'; hence, to deprive a law of force by opinions or acts opposed to it, to transgress it, Mark 7:9; Hebrews 10:28 (Ezekiel 22:26); πίστιν, to break one's promise or engagement, 1 Timothy 5:12; (Polybius 8, 2, 5; 11, 29, 3, others; Diodorus excerpt. (i. e.de virt. et vit.), p. 562, 67). Hence,
b. to thwart the efficacy of anything, nullify, make void?, frustrate: τήν βουλήν τοῦ Θεοῦ, Luke 7:30 (they rendered inefficacious the saving purpose of God); τήν συνέσω to render prudent plans of no effect, 1 Corinthians 1:19 (Isaiah 29:14 (where κρύψω, yet cf. Bos's note)).
c. to reject, refuse, slight; τήν χάριν τοῦ Θεοῦ, Galatians 2:21 (others refer this to b.); of persons: Mark 6:26 (by breaking the promise given her); Luke 10:16; John 12:48; 1 Thessalonians 4:8; Jude 1:8 (for which καταφρόνειν is used in the parallel passage 2 Peter 2:10). (For examples of the use of this word see Sophocles' Lexicon, under the word.)