{ Æ*ol"i*pile, Æ*ol"i*pyle } (&?;), n. [L. aeolipilae; Aeolus god of the winds + pila a ball, or Gr. &?; 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.]

&fist; Such an apparatus was first described by Hero of Alexandria about 200 years b. c. It has often been called the first steam engine.

• an instrument used to demonstrate the force at which heated vapour escapes from a vessel through a narow aperture