guest vs overnighter

guest and overnighter both are nouns.

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

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

Other hyponyms of guest include no-show.

guest (noun)	overnighter (noun)
(computer science) any computer that is hooked up to a computer network	a small traveling bag to carry clothing and accessories for staying overnight
a visitor to whom hospitality is extended	a guest who stays overnight
a customer of a hotel or restaurant etc.