silhouette vs outline

silhouette and outline both are nouns.

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

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

Other hypernyms of silhouette include lineation.

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

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