adj.
Pronunciation: ' tha ŋ k-l ə s
Function: adjective
Date: 15th century
1 : not likely to obtain thanks : UNAPPRECIATED <a thankless task>
2 : not expressing or feeling gratitude : UNGRATEFUL <how sharper than a serpent's tooth it is to have a thankless child ― Shakespeare>
– thank · less · ly adverb
– thank · less · ness noun