Superlative form of cranky; the most bad-tempered or difficult to please.
From cranky + -iest (superlative suffix). The threefold intensity marker on an already negative trait—the furthest degree of irritability.
Babies are actually crankiest around 6 weeks old, right when their circadian rhythms are developing—it's not random crankiness but their brains literally rewiring their sleep-wake cycles.
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