runner-up finish vs second-place finish

runner-up finish and second-place finish both are nouns.

Word	Noun	Adjective	Verb	Adverb
runner-up finish	Yes	No	No	No
second-place finish	Yes	No	No	No

As nouns, runner-up finish and second-place finish are synonyms defined as:

runner-up finish and second-place finish: a finish in second place (as in a race)

runner-up finish (noun)	second-place finish (noun)
a finish in second place (as in a race)	a finish in second place (as in a race)