cnidarian vs medusan

cnidarian and medusan both are nouns.

Word	Noun	Adjective	Verb	Adverb
cnidarian	Yes	No	No	No
medusan	Yes	No	No	No

As nouns, medusan is a hyponym of cnidarian; that is, medusan is a word with a more specific, narrower meaning than cnidarian:

cnidarian: radially symmetrical animals having saclike bodies with only one opening and tentacles with stinging structures; they occur in polyp and medusa forms
medusan: one of two forms that coelenterates take: it is the free-swimming sexual phase in the life cycle of a coelenterate; in this phase it has a gelatinous umbrella-shaped body and tentacles

Other hyponyms of cnidarian include polyp, medusa, medusoid, jellyfish, scyphozoan, hydroid, hydrozoan, actinozoan, anthozoan.

cnidarian (noun)	medusan (noun)
radially symmetrical animals having saclike bodies with only one opening and tentacles with stinging structures; they occur in polyp and medusa forms	one of two forms that coelenterates take: it is the free-swimming sexual phase in the life cycle of a coelenterate; in this phase it has a gelatinous umbrella-shaped body and tentacles