outline vs coastline

outline and coastline both are nouns.

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

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

Other hyponyms of outline include profile, silhouette, skyline.

outline (noun)	coastline (noun)
a schematic or preliminary plan	the outline of a coast
a sketchy summary of the main points of an argument or theory
the line that appears to bound an object

outline (verb)	coastline (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