Noah Webster's Dictionary 1. (a.) Not acknowledging favors; not expressing thankfulness; unthankful; ungrateful. 2. (a.) Not obtaining or deserving thanks; unacceptable; as, a thankless task.

Multi-Version Concordance Thankless (1 Occurrence) 2 Timothy 3:2 For men will be lovers of self, lovers of money, boastful, haughty, profane. They will be disobedient to parents, thankless, irreligious, (WEY)