thank·less /ˈθæŋkləs/
 (a.)不感謝的,忘恩的,不知感恩的
 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.
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 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]