Here's what rhymes with castiest.
theist shiest sliest pastiest gaudiest wiliest puniest gamiest chariest fruitiest crispiest messiest corniest sultriest mangiest untidiest laciest scaliest tangiest unhandiest mousiest paltriest wintriest unwariest unloveliest unmanliest Words that almost rhyme with castiest
deepest cheapest chiefest steepest decent sweetest weakest keenest leant meanest peanut antient briefest piquant tliat neatest sapient bleakest fleetest meekest sheerest leanest serenest realest sleekest liefest serest recent regent sentient sicut machinist seulement cleanest licit sealant completest reshipped beechnut meagerest reedit obscenest woodenest treatment agreement secret achievement frequent bereavement indecent appeasement decedent leaflet sequenced bafflement orthopedist preachment seafront pointillist orthopaedist uncleanest convenient concealment impeachment mendicant benignant insentient discreetest pantomimist cajolement infrequent maltreatment defilement mistreatment disablement enfeeblement impalement enjambement beguilement revilement disagreement inconvenient pretreatment inconvenienced underachievement ennoblement regalement intercollegiate