rundown vs summing up

rundown and summing up both are nouns.

Word	Noun	Adjective	Verb	Adverb
rundown	Yes	No	No	No
summing up	Yes	No	No	No

As nouns, rundown and summing up are synonyms defined as:

rundown and summing up: a concluding summary (as in presenting a case before a law court)

Other synonyms of rundown include summation.

rundown (noun)	summing up (noun)
a concluding summary (as in presenting a case before a law court)	a concluding summary (as in presenting a case before a law court)