{ } n. [ L. aeolipilae; Aeolus god of the winds + pila a ball, or Gr. &unr_; gate (i. e., doorway of Æolus); cf. F. éolipyle. ] An apparatus consisting chiefly of a closed vessel (as a globe or cylinder) with one or more projecting bent tubes, through which steam is made to pass from the vessel, causing it to revolve. [ Written also eolipile. ] [ 1913 Webster ]

☞ Such an apparatus was first described by Hero of Alexandria about 200 years b. c. It has often been called the first steam engine. [ 1913 Webster ]