D defs.my
Entry 2 senses Webster, 1913

Thankless

· Thank·less · IPA /θˈæŋkləs/
01 a. Not acknowledging favors; not expressing thankfulness; unthankful; ungrateful.
  1. 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. 2.
    Not obtaining or deserving thanks; unacceptable; as, a thankless task.
    “To shepherd thankless, but by thieves that love the night allowed.” Chapman.