Longman Dictionary of Contemporary English
Wiktionary
n. Any dance traditionally performed by the common people of a specific region.
WordNet
n. a style of dancing that originated among ordinary people (not in the royal courts) [syn: folk dancing]
v. perform a folk-dance
Wikipedia
Folk dances are dances developed by groups of people that reflect the traditional life of the people of a certain country or region. Not all ethnic dances are folk dances; for example, ritual dances or dances of ritual origin are not considered to be folk dances. Ritual dances are usually called "Religious dances" because of their purpose.
The terms "ethnic" and "traditional" are used when it is required to emphasize the cultural roots of the dance. In this sense, nearly all folk dances are ethnic ones. If some dances, such as polka, cross ethnic boundaries and even cross the boundary between "folk" and "ballroom dance", ethnic differences are often considerable enough to mention, e.g., Czech polka vs. German polka.
Usage examples of "folk dance".
His buddies each invited a barmaid to dance, and they all did a peasant couple dance, and then another folk dance, which progressed off stage.
I think people would be much happier in a regulated society that had a definite pattern and a unified form--like a folk dance.