skyline vs visible horizon

skyline and visible horizon both are nouns.

Word	Noun	Adjective	Verb	Adverb
skyline	Yes	No	No	No
visible horizon	Yes	No	No	No

As nouns, skyline and visible horizon are synonyms defined as:

skyline and visible horizon: the line at which the sky and Earth appear to meet

Other synonyms of skyline include apparent horizon, horizon, sensible horizon.

skyline (noun)	visible horizon (noun)
the line at which the sky and Earth appear to meet	the line at which the sky and Earth appear to meet
the outline of objects seen against the sky