The Collaborative International Dictionary of English v.0.48:

Jenny \Jen"ny\, n. [A corruption of gin an engine; influenced by
   Jenny, the proper name. See Gin an engine, and cf.
   Ginny-carriage.]
   A machine for spinning a number of threads at once, -- used
   in factories. Also called spinning jenny.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Spinning \Spin"ning\,
   a. & n. from Spin.
   [1913 Webster]

   Spinning gland (Zool.), one of the glands which form the
      material for spinning the silk of silkworms and other
      larvae.

   Spinning house, formerly a common name for a house of
      correction in England, the women confined therein being
      employed in spinning.

   Spinning jenny (Mach.), an engine or machine for spinning
      wool or cotton, by means of a large number of spindles
      revolving simultaneously.

   Spinning mite (Zool.), the red spider.

   Spinning wheel, a machine for spinning yarn or thread, in
      which a wheel drives a single spindle, and is itself
      driven by the hand, or by the foot acting on a treadle.
      [1913 Webster]

WordNet (r) 3.0 (2006):

spinning jenny
    n 1: an early spinning machine with multiple spindles