Merriam-Webster Collegiate Dictionary - rondeau

 noun  (plural ~x)  Etymology: Middle French rondel, ~  Date: 1525  1.  a. a fixed form of verse based on two rhyme sounds and consisting usually of 13 lines in three stanzas with the opening words of the first line of the first stanza used as an independent refrain after the second and third stanzas  b. a poem in this form  2. a monophonic trouvere song with a 2-part refrain