estimate vs lowball

estimate is a noun but lowball is not a noun.

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

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

estimate (noun)	lowball (noun)
a judgment of the qualities of something or somebody
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)	lowball (verb)
judge tentatively or form an estimate of (quantities or time)	make a deliberately low estimate
judge to be probable