Real Dictionary

Main Street
proper noun: In small towns in the United States, the street where most of the shops are is often called Main Street.
uncountable noun: Main Street is used by journalists to refer to the ordinary people of America who live in small towns rather than big cities or are not very rich.

Main Street in British English
the principal street of any small town
the principal thoroughfare, esp. through the business district, in a small town
noun: the most prominent street of a town, usually where the principal shops and businesses are situated

Main Street in Retail
noun: a novel (1920) by Sinclair Lewis
noun: Main Street is used to refer to the most important shopping street in the traditional center of towns and cities, and to the brand name stores typically found there.