Wiktionary
unthankful
a. Not thankful; ungrateful.
WordNet
unthankful
adj. not feeling or showing gratitude; "ungrateful heirs"; "How sharper than a serpent's tooth it is / To have a thankless child!"- Shakespeare [syn: ungrateful, thankless] [ant: grateful]
Usage examples of "unthankful".
I think there is not one among us all, either so disobedient a subject in regard of our duty, or so unthankful a man in respect of the inestimable benefits which by her or from her we have received, which would not with frank consent, both of voice and heart, most willingly submit himself thereunto, without any unreverend inquiry into the causes thereof.