outline vs skyline

outline and skyline both are nouns.

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

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

Other hyponyms of outline include coastline, profile, silhouette.

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

outline (verb)	skyline (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