ungrateful
adj.not feeling or showing thanks for something kind that someone has done for you.
adj.failing to acknowledge or express appreciation for benefits received. Often used to describe a person's character or a specific reaction to a gift or favor.
“He felt his children were being ungrateful for their gifts.”
“She didn't want to sound ungrateful, but the sweater her aunt knitted was three sizes too large.”
“The politician's refusal to acknowledge his early supporters was seen as an ungrateful gesture that eventually cost him the loyalty of his core constituency.”
Often follows a linking verb like 'be', 'seem', or 'feel'; frequently takes the preposition 'for' to indicate the cause of the gratitude.
Use 'to' for the person who gave the gift, but 'for' for the gift itself.
From un- + grateful.
Etymology adapted from Wiktionary, available under CC BY-SA 4.0.