Brevity rhymes with:
longevity, activity, captivity, cavity, conductivity, creativity, depravity, exclusivity, festivity, gravity, insensitivity, longevity, mcavity, nativity, negativity, proclivity, productivity, progressivity, radioactivity, reactivity, relativity, selectivity, superconductivity, velvety
Brevity sounds like:
barbato, barbed, barbette, barbuda, barefoot, barfoot, bereaved, bereft, bravado, braved, bribed, briefed, browbeat