Here's what rhymes with costrum.
nostrum rostrum Words that almost rhyme with costrum
autumn awesome carom bottom column quantum forum mortem quorum condom possum cockscomb solemn blossom boredom decorum balsam dorsum sorghum bonum wampum flotsam opossum foursome problem drachm stardom thraldom slalom thralldom sugarplum postpartum metronome gastronome microcosm falciparum macrocosm