Superlative form of cheery: most cheery.(adjective)
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Use "cheeriest" in a sentence
"A few days before Russia responded to the E coli scare with a heavy-handed bar on all sorts of European vegetable imports, the cheeriest thing America's top trade official could find to say about the Doha round was that he was not ready to read the last rites over its corpse."
"I gave each of them my cheeriest smile and a friendly greeting, and for the most part was met with cool indifference."
"“Good morning, sexy,” I sang out in the cheeriest voice I could manage."