Answer: nippiest

AnswerCrossword Clue
NIPPIESTLeast suited to beachwear
NIPPIESTMost invigorating.
NIPPIESTMost chilly
nippiest(of the weather) Rather cold; chilly
nippiestInclined to nip or bite
nippiestNIPPY, quick (speedy (swift (speedy)))
nippiestQuick; nimble