closing vs windup

closing and windup both are nouns.

Word	Noun	Adjective	Verb	Adverb
closing	Yes	Yes	No	No
windup	Yes	Yes	No	No

As nouns, closing and windup are synonyms defined as:

Other synonyms of closing include completion, culmination, mop up.

closing (noun)	windup (noun)
termination of operations	a concluding action
the act of closing something
a concluding action
approaching a particular destination; a coming closer; a narrowing of a gap
the last section of a communication

closing (adjective)	windup (adjective)
final or ending	operated by a mechanism