Here's what rhymes with impermanent.

Consider these alternatives

nonmagnetic / magnetic biocompatible / capital corporeal / territorial genteelly / freely mutable / suitable incorporeal / territorial ahistorical / historical insubstantial / sample unpractical / practical metaphysically / physically immaterial / material irretrievable / feasible ephemeral / general juxtapositions / conditions biodegradability / stability immutable / suitable illusionary / very