G0884
ἀχάριστος
ungrateful
ἀχάριστος, -ον (χαρίζομαι), [in LXX: Wis.16:29, Sir.29:17, 25, 4Ma.9:10 * ;] __(a) ungracious, unpleasing; __(b) ungrateful, thankless: Luk.6:35, 2Ti.3:2.† (AS)
Full Thayer's lexicon entry
ἀχάριστος — acháristos
ἀχάριστος, ἀχαριστον (χαρίζομαι), ungracious;
a. unpleasing (Homer, Odyssey 8, 236; 20, 392; Xenophon, oec. 7, 37; others).
b. unthankful (so in Greek writings from Herodotus 1, 90 down): Luk 6:35; 2Ti 3:2. (Sir 29:17; Wis 16:29.)
2 occurrences
Luke (1), II Timothy (1)