1. Not feeling or showing gratitude
   "How sharper than a serpent's tooth it is / To have a thankless child!"
   - ungrateful, unthankful 
2. Not likely to be rewarded
   "grading papers is a thankless task"
   - unappreciated, ungratifying

See also: unappreciative, unrewarding

• cheerly
• cheers
• cheery
• cheese
• cheese cutter
• cheese dip
• cheese fondue
• cheese pizza
• cheese press
• cheese rind
• cheese sauce
• cheese souffle
• cheese spread
• cheese straw
• cheese tray
• cheeseboard
• cheeseburger
• cheesecake
• cheesecloth
• cheesed off
• cheeseflower
• cheeselike
• cheesemonger
• cheeseparing
• cheesiness