The most neat, trim, and fashionable in appearance; the superlative form of dapper.
From 'dapper' plus the superlative suffix '-est'; follows standard English morphology for forming superlatives from one-syllable adjectives.
The superlative dapperest is rarely used in modern English, but it reminds us that we once had more colorful ways to describe extreme neatness—now we'd say 'most dapper,' showing how English is losing some of its morphological variety.
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