duckbill vs duck-billed

duckbill is a noun but duck-billed is not a noun.

Word	Noun	Adjective	Verb	Adverb
duckbill	Yes	Yes	No	No
duck-billed	No	Yes	No	No

As adjectives, duckbill and duck-billed are synonyms defined as:

duckbill (noun)	duck-billed (noun)
small densely furred aquatic monotreme of Australia and Tasmania having a broad bill and tail and webbed feet; only species in the family Ornithorhynchidae
primitive fish of the Mississippi valley having a long paddle-shaped snout

duckbill (adjective)	duck-billed (adjective)
having a beak resembling that of a duck	having a beak resembling that of a duck