field day vs picnic

field day and picnic both are nouns.

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

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

Other synonyms of field day include outing.

field day (noun)	picnic (noun)
a day for outdoor athletic competition	any undertaking that is easy to do
a day devoted to an outdoor social gathering	any informal meal eaten outside or on an excursion
(military) a day for military exercises and display	a day devoted to an outdoor social gathering
a time of unusual pleasure and success

field day (verb)	picnic (verb)
	eat alfresco, in the open air