Perplexity rhymes with:
complexity, complexity, complexity, complexity, laxity, analyticity, animosity, atrocity, audacity, biodiversity, capacity, complexity, complicity, curiosity, density, diversity, domesticity, eccentricity, elasticity, electricity, falsity, felicity, ferocity, generosity, incapacity, intensity, laxity, monstrosity, necessity, obesity, opacity, overcapacity, paucity, perversity, publicity, religiosity, simplicity, specificity, toxicity, university, velocity, viscosity, voracity
Perplexity sounds like:
perplexed, privileged, profligate