Harshness rhymes with:
bearishness, boorishness, brashness, bullishness, foolishness, freshness, jewishness, selfishness, skittishness, sluggishness, squeamishness, waterishness
Harshness sounds like:
harassing, hargens, harkin's, harking, harkins, harkness, harrison's, hearkens, herzing, hirosakamoki, hoarseness, horizon's, horizons, horsham's, horsing, hurricane's, hurricanes