The Collaborative International Dictionary of English v.0.48:

Triolet \Tri"o*let\ (tr[imac]"[-o]*l[e^]t), n. [F. triolet. See
   Trio.]
   A short poem or stanza of eight lines, in which the first
   line is repeated as the fourth and again as the seventh line,
   the second being, repeated as the eighth. --Brande & C.
   [1913 Webster]