estimate vs guessing

estimate and guessing both are nouns.

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

As nouns, guessing is a hyponym of estimate; that is, guessing is a word with a more specific, narrower meaning than estimate:

estimate (noun)	guessing (noun)
a judgment of the qualities of something or somebody	an estimate based on little or no information
an approximate calculation of quantity or degree or worth
the respect with which a person is held
a document appraising the value of something (as for insurance or taxation)
a statement indicating the likely cost of some job

estimate (verb)	guessing (verb)
judge tentatively or form an estimate of (quantities or time)
judge to be probable