Main entry: thankless, ungrateful, unthankful
Definition: not feeling or showing gratitude
Usage: ungrateful heirs; How sharper than a serpent's tooth it is / To have a thankless child!- Shakespeare
Main entry: unappreciated, ungratifying, thankless
Definition: not likely to be rewarded
Usage: grading papers is a thankless task
Antonyms: rewarding
Definition: providing personal satisfaction