guesswork vs guessing

guesswork and guessing both are nouns.

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

As nouns, guesswork and guessing are synonyms defined as:

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

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