adj.吃力不讨好的;徒劳无功的;<罕>不表示感谢的;不受人注意的;
例句:
Don't tell him, Joe, that I was thankless.
乔, 你可千万别告诉他说我是个志恩负义的人呀.
How sharper than a serpent's tooth is to have a thankless child . ( William Shakespeare, British dramatist )
逆子无情甚于蛇蝎. ( 英国剧作家莎士比亚 )
BEING a Middle East peace envoy is a thankless task.
做一个中东和平使者是一项不讨好的任务.