main vs offing

main and offing both are nouns.

Word	Noun	Adjective	Verb	Adverb
main	Yes	Yes	No	No
offing	Yes	No	No	No

main (noun)	offing (noun)
a principal pipe in a system that distributes water or gas or electricity or that collects sewage	the part of the sea that can be seen from the shore and is beyond the anchoring area
any very large body of (salt) water	the near or foreseeable future

main (adjective)	offing (adjective)
(of a clause) capable of standing syntactically alone as a complete sentence
most important element
of force; of the greatest possible intensity