thank·less / ˈ[unvoicedth]angklis/ • adj. (of a job or task) difficult or unpleasant and not likely to bring one pleasure or the appreciation of others. ∎ (of a person) not expressing or feeling gratitude. DERIVATIVES: thank·less·ly adv. thank·less·ness n.
"thankless." The Oxford Pocket Dictionary of Current English. . Encyclopedia.com. (January 22, 2019). https://www.encyclopedia.com/humanities/dictionaries-thesauruses-pictures-and-press-releases/thankless
"thankless." The Oxford Pocket Dictionary of Current English. . Retrieved January 22, 2019 from Encyclopedia.com: https://www.encyclopedia.com/humanities/dictionaries-thesauruses-pictures-and-press-releases/thankless