Third-person singular simple present indicative form of mellow.(verb)
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Use "mellows" in a sentence
"If there is frost during the winter both farmer and gardener are pleased because they say the frost "mellows" the ground; you can see what they mean if you walk on a frosty morning over a ploughed field."
"Zardari 'mellows' after US nudge to put Pak on track"
"Taste the sauce, add tiny amounts of baking soda to see if it mellows the acidity."