outline vs silhouette

outline and silhouette both are nouns.

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

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

Other hyponyms of outline include coastline, profile, skyline.

outline (noun)	silhouette (noun)
a schematic or preliminary plan	a drawing of the outline of an object; filled in with some uniform color
a sketchy summary of the main points of an argument or theory	an outline of a solid object (as cast by its shadow)
the line that appears to bound an object

outline (verb)	silhouette (verb)
describe roughly or briefly or give the main points or summary of	represent by a silhouette
trace the shape of	project on a background, such as a screen, like a silhouette
draw up an outline or sketch for something