Superlative form of finicky; most fussy, picky, or hard to please; extremely particular about details.
From finicky (adjective) plus -est suffix forming the superlative degree. This is the highest degree of comparison, indicating the maximum level of fussiness or particularity.
The 'finickiest' person you know probably drives you crazy, but science suggests they have stronger sensory perception—they might literally taste, smell, and see things more intensely than others, making their pickiness not rudeness but neurology!
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