the GNU version of the Collaborative International Dictionary of English
adj. Not acknowledging favors; not expressing thankfulness; unthankful; ungrateful.
adj. Not obtaining or deserving thanks; unacceptable.
The Century Dictionary and Cyclopedia
Unthankful; ungrateful; not acknowledging kindness or benefits.
Not deserving thanks, or not likely to be rewarded with thanks: as, a thankless task.
Synonyms See grateful.
WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
adj. not feeling or showing gratitude
adj. not likely to be rewarded
Word Usage
"That being said, natural charisma goes a long way and even in thankless, underwritten parts, my biggest complaint was that I wanted to see more of the characters."