skyline vs outline

skyline and outline both are nouns.

Word	Noun	Adjective	Verb	Adverb
skyline	Yes	No	No	No
outline	Yes	No	Yes	No

As nouns, outline is a hypernym of skyline; that is, outline is a word with a broader meaning than skyline:

Other hypernyms of skyline include lineation.

skyline (noun)	outline (noun)
the line at which the sky and Earth appear to meet	a schematic or preliminary plan
the outline of objects seen against the sky	a sketchy summary of the main points of an argument or theory
	the line that appears to bound an object

skyline (verb)	outline (verb)
	describe roughly or briefly or give the main points or summary of
	trace the shape of
	draw up an outline or sketch for something