sign off vs cease

sign off is not a noun while cease is a noun.

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

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

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

sign off (noun)	cease (noun)
	(`cease' is a noun only in the phrase `without cease') end

sign off (verb)	cease (verb)
cease broadcasting; get off the air; as of radio stations	put an end to a state or an activity
	have an end, in a temporal, spatial, or quantitative sense; either spatial or metaphorical