The Collaborative International Dictionary of English v.0.48:

Roundelay \Round"e*lay\, n. [OF. rondelet, dim. of rondel. See
   Roundel, Roundeau, and cf. Roundlet, Rundlet.]
   1. (Poetry) See Rondeau, and Rondel.
      [1913 Webster]

   2. (Mus.)
      (a) A tune in which a simple strain is often repeated; a
          simple rural strain which is short and lively.
          --Spenser. --Tennyson.
      (b) A dance in a circle.
          [1913 Webster]

   3. Anything having a round form; a roundel.
      [1913 Webster]

WordNet (r) 3.0 (2006):

roundelay
    n 1: a song in which a line or phrase is repeated as the refrain