corn cob vs corncob

corn cob and corncob both are nouns.

Word	Noun	Adjective	Verb	Adverb
corn cob	Yes	No	No	No
corncob	Yes	No	No	No

As nouns, corn cob and corncob are synonyms defined as:

corn cob and corncob: the hard cylindrical core that bears the kernels of an ear of corn

corn cob (noun)	corncob (noun)
the hard cylindrical core that bears the kernels of an ear of corn	the hard cylindrical core that bears the kernels of an ear of corn