gridiron vs football field

gridiron and football field both are nouns.

Word	Noun	Adjective	Verb	Adverb
gridiron	Yes	No	No	No
football field	Yes	No	No	No

As nouns, gridiron and football field are synonyms defined as:

gridiron and football field: the playing field on which football is played

gridiron (noun)	football field (noun)
a cooking utensil of parallel metal bars; used to grill fish or meat	the playing field on which football is played
the playing field on which football is played