guessing vs guesswork

guessing and guesswork both are nouns.

Word	Noun	Adjective	Verb	Adverb
guessing	Yes	No	No	No
guesswork	Yes	No	No	No

As nouns, guessing and guesswork are synonyms defined as:

Other synonyms of guessing include dead reckoning, guess, shot.

guessing (noun)	guesswork (noun)
an estimate based on little or no information	an estimate based on little or no information