1. superlative form of mellow: most relaxed, calm, or easygoing
Usage: informal
2. superlative form of mellow: having the smoothest, richest, or most pleasant sound or taste

Examples

• He’s the mellowest person I know, never getting upset about anything.
• This is the mellowest jazz album in my collection.
• The wine becomes mellowest after aging for several years.
• She has the mellowest voice of all the singers.
• That’s the mellowest coffee blend they serve.
• He was at his mellowest during the vacation.