guess vs lowball

guess is a noun but lowball is not a noun.

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

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

guess (noun)	lowball (noun)
an estimate based on little or no information
a message expressing an opinion based on incomplete evidence

guess (verb)	lowball (verb)
expect, believe, or suppose	make a deliberately low estimate
judge tentatively or form an estimate of (quantities or time)
guess correctly; solve by guessing
put forward, of a guess, in spite of possible refutation