Villanelle: One of the French fixed forms. Originally pastoral in subject matter (the name derives from villa, a farm or country house), it is often used for light verse. There are five tercets followed by a quatrain, all on two rhymes. The opening line is repeated at the ends of tercets two and four; the final line of the first tercet concludes the third and fifth. The two refrain lines are repeated at the end of the quatrain.

(Beckson & Ganz, Literary Terms: A Dictionary, 298)