overrun vs overflow

overrun and overflow both are nouns.

Word	Noun	Adjective	Verb	Adverb
overrun	Yes	No	Yes	No
overflow	Yes	No	Yes	No

As verbs, overrun and overflow are synonyms defined as:

Other synonyms of overrun include brim over, run over, well over.

overrun (noun)	overflow (noun)
too much production or more than expected	a large flow
	the occurrence of surplus liquid (as water) exceeding the limit or capacity

overrun (verb)	overflow (verb)
run beyond or past	overflow with a certain feeling
seize the position of and defeat	flow or run over (a limit or brim)
flow or run over (a limit or brim)
invade in great numbers
occupy in large numbers or live on a host