visitor vs guest

visitor and guest both are nouns.

Word	Noun	Adjective	Verb	Adverb
visitor	Yes	No	No	No
guest	Yes	No	No	No

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

Other hyponyms of visitor include boulevardier, caller, company, invitee, visiting fireman.

visitor (noun)	guest (noun)
someone who visits	(computer science) any computer that is hooked up to a computer network
	a visitor to whom hospitality is extended
	a customer of a hotel or restaurant etc.