Other forms: populously
A populous place is full of people. If you left your cabin in the Maine woods to spend the weekend in New York City, you'd be particularly aware of how populous the city is.
Anything that's dense with people can be described as populous, like the country of China or the city of Mumbai or even a crowded airport. Populous is a Latin word that means simply "people." It was adopted by English in the 15th century to mean "full of people." The adjective populous is easy to confuse with the noun populace, "the people who live in a country," especially since they are homonyms, or words that sound exactly the same.