The Collaborative International Dictionary of English v.0.48:

Ingrateful \In"grate`ful\, a. [L. ingratus ingrateful (pref. in-
   not + gratus beloved, dear, grateful) + -ful: cf. F. ingrat.
   See Grateful.]
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   1. Ungrateful; thankless; unappreciative. --Milton.
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            He proved extremely false and ingrateful to me.
                                                  --Atterbury.
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   2. Unpleasing to the sense; distasteful; offensive.
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            He gives . . . no ingrateful food.    --Milton.
      -- In"grate`ful*ly, adv. -- In"grate`ful*ness, n.
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