city limits vs city limit

city limits and city limit both are nouns.

Word	Noun	Adjective	Verb	Adverb
city limits	Yes	No	No	No
city limit	Yes	No	No	No

As nouns, city limits and city limit are synonyms defined as:

city limits and city limit: the limits of the area occupied by a city or town

city limits (noun)	city limit (noun)
the limits of the area occupied by a city or town	the limits of the area occupied by a city or town