Superlative form of hearty: most hearty.(adjective)
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Use "heartiest" in a sentence
"In her message conveying her "heartiest" wishes on the International"
"Dear Smokey B Dokey, Maxine and I send you our heartiest wishes for quick recovery from the snip-snipping and know that you will be just peachy soon."
"My heartiest amazement to those of you who have done this more than once."