sign off vs quit

sign off and quit both are verbs.

Word	Noun	Adjective	Verb	Adverb
sign off	No	No	Yes	No
quit	No	No	Yes	No

As verbs, quit is a hypernym of sign off; that is, quit is a word with a broader meaning than sign off:

Other hypernyms of sign off include cease, discontinue, give up, lay off, stop.

sign off (verb)	quit (verb)
cease broadcasting; get off the air; as of radio stations	give up in the face of defeat of lacking hope; admit defeat
	go away or leave
	turn away from; give up
	give up or retire from a position
	put an end to a state or an activity