outflow vs natural spring

outflow and natural spring both are nouns.

Word	Noun	Adjective	Verb	Adverb
outflow	Yes	No	No	No
natural spring	Yes	No	No	No

As nouns, outflow and natural spring are synonyms defined as:

Other synonyms of outflow include fountain, outpouring, spring.

outflow (noun)	natural spring (noun)
the discharge of a fluid from some container	a natural flow of ground water
a natural flow of ground water
the process of flowing out