Unpleasing; unacceptable; disagreeable; as, harsh sounds are ungrateful to the ear.

disagreeable; "I will not perform the ungrateful task of comparing cases of failure"- Abraham Lincoln

not feeling or showing gratitude; "ungrateful heirs"; "How sharper than a serpent's tooth it is / To have a thankless child!"- Shakespeare

Not grateful; not thankful for favors; making no returns, or making ill return for kindness, attention, etc.; ingrateful.