Synonyms:
ungrateful, thankless, unthankful
Meaning: not feeling or showing gratitude; "ungrateful heirs"; "How sharper than a serpent's tooth it is / To have a thankless child!"- Shakespeare
Synonyms:
thankless, unappreciated, ungratifying
Meaning: not likely to be rewarded; "grading papers is a thankless task"
Usage examples
It was a thankless job at best, and full of hardship and danger.
One morning we left the cold and snow, where we had lived and shivered in thin tents all the winter, left the thankless duty of patrolling railroads in the storm at midnight, and marched in the direction of St. Louis.
Russell Square was the boundary of her prison: she might walk thither occasionally, but was always back to sleep in her cell at night; to perform cheerless duties; to watch by thankless sick-beds; to suffer the harassment and tyranny of querulous disappointed old age.