thankless

adjective

1 a thankless task:

unappreciated, unrecognized, unrewarded, unacknowledged;

unenviable, difficult, unpleasant, unrewarding, unprofitable, profitless, useless, fruitless, vain, futile;

archaic bootless.

▷antonyms rewarding, worthwhile.

2 her thankless children:

ungrateful, unappreciative, unthankful.

▷antonyms grateful.

thankless Oxford Dictionary of English