estimate vs guesstimate

estimate and guesstimate both are nouns.

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

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

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

Other hyponyms of estimate include quantise, quantize, misgauge, place, put, set, give, lowball, underestimate, assess, make, count, reckon, truncate.

estimate (noun)	guesstimate (noun)
a judgment of the qualities of something or somebody	an estimate that combines reasoning with guessing
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)	guesstimate (verb)
judge tentatively or form an estimate of (quantities or time)	estimate based on a calculation
judge to be probable