资料来源 : pyDict

不感谢的,忘恩的,不知感恩的

资料来源 : Webster's Revised Unabridged Dictionary (1913)

Thankless \Thank"less\, a.
   1. Not acknowledging favors; not expressing thankfulness;
      unthankful; ungrateful.

            That she may feel How sharper than a serpent's tooth
            it is To have a thankless child!      --Shak.

   2. Not obtaining or deserving thanks; unacceptable; as, a
      thankless task.

            To shepherd thankless, but by thieves that love the
            night allowed.                        --Chapman.
      -- {Thank"less*ly}, adv. -- {Thank"less*ness}, n.

资料来源 : WordNet®

thankless
     adj 1: not feeling or showing gratitude; "ungrateful heirs"; "How
            sharper than a serpent's tooth it is / To have a
            thankless child!"- Shakespeare [syn: {ungrateful}, {unthankful}]
            [ant: {grateful}]
     2: not likely to be rewarded; "grading papers is a thankless
        task" [syn: {unappreciated}, {ungratifying}]