outline vs sketch out

outline is a noun but sketch out is not a noun.

Word	Noun	Adjective	Verb	Adverb
outline	Yes	No	Yes	No
sketch out	No	No	Yes	No

As verbs, sketch out is a hyponym of outline; that is, sketch out is a word with a more specific, narrower meaning than outline:

Other hyponyms of outline include block out.

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

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