The Collaborative International Dictionary of English v.0.48:

Singspiel \Sing"spiel`\, n. [G.; singen to sing + spiel to
   play.] (Music)
   A dramatic work, partly in dialogue and partly in song, of a
   kind popular in Germany in the latter part of the 18th
   century. It was often comic, had modern characters, and
   patterned its music on folk song with strictly subordinated
   accompaniment.
   [Webster 1913 Suppl.]