To humour; to induce the opposite effect of causing a person to become disgruntled.(verb)
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Use "gruntle" in a sentence
"The OED and Merriam-Webster list that play on a word as a back-formation from disgruntle, and the word gruntle is born again—meaning “to put in a good humor.”"
"There is a little more about it here, where you can also read a short history of gruntle."
"Haow duz he getz hiz gruntle bak? ai nebbur did unnurstan dat. just wut iz a gruntle?"