Softballs rhymes with:
basketball's, basketballs, fastballs, football's, footballs, meatballs, spitball's, basketball's, basketballs, butterballs, eyeballs, fastballs, fireballs, football's, footballs, handballs, meatballs, mothballs, oddballs, snowball's, snowballs, spaceballs, spitball's, trackballs