cattle guard vs cattle grid

cattle guard and cattle grid both are nouns.

Word	Noun	Adjective	Verb	Adverb
cattle guard	Yes	No	No	No
cattle grid	Yes	No	No	No

As nouns, cattle guard and cattle grid are synonyms defined as:

cattle guard and cattle grid: a bridge over a ditch consisting of parallel metal bars that allow pedestrians and vehicles to pass, but not cattle

cattle guard (noun)	cattle grid (noun)
a bridge over a ditch consisting of parallel metal bars that allow pedestrians and vehicles to pass, but not cattle	a bridge over a ditch consisting of parallel metal bars that allow pedestrians and vehicles to pass, but not cattle