noun
ingrate
IN-grayt/ˈɪnˌɡreɪt/
A person who shows no gratitude.
The ingrate turns dismissively away from the person returning the lost belongings.

Etymology
The combination meaning “not pleasing” also carried the Latin sense “ungrateful.” English used it as an adjective before making it a noun for someone who fails to show thanks.
In context
You're such an ingrate! We wasted twenty years raising you!
More examples
- Don't be an ingrate; thank your sister for the ride.
- They called us ingrates because we never thanked them.
- Only an ingrate would mock such a thoughtful gift.
Forms
ingrate · ingrates
ingratitude noun — Failure to appreciate kindness or help.
Similar words
- ungrateful person
- A less pointed description; ingrate more strongly condemns the person.