field day vs outing

field day and outing both are nouns.

Word	Noun	Adjective	Verb	Adverb
field day	Yes	No	No	No
outing	Yes	No	No	No

As nouns, field day and outing are synonyms defined as:

Other synonyms of field day include picnic.

field day (noun)	outing (noun)
a day for outdoor athletic competition	a journey taken for pleasure
a day devoted to an outdoor social gathering	a day devoted to an outdoor social gathering
(military) a day for military exercises and display
a time of unusual pleasure and success