The Collaborative International Dictionary of English v.0.48:

jumper \jump"er\ (j[u^]mp"[~e]r), n.
   1. One who, or that which, jumps.
      [1913 Webster]

   2. A long drilling tool used by masons and quarrymen.
      [1913 Webster]

   3. A rude kind of sleigh; -- usually, a simple box on runners
      which are in one piece with the poles that form the
      thills. [U.S.] --J. F. Cooper.
      [1913 Webster]

   4. (Zool.) The larva of the cheese fly. See Cheese fly,
      under Cheese.
      [1913 Webster]

   5. (Eccl.) A name applied in the 18th century to certain
      Calvinistic Methodists in Wales whose worship was
      characterized by violent convulsions.
      [1913 Webster]

   6. (Horology) spring to impel the star wheel, also a pawl to
      lock fast a wheel, in a repeating timepiece.
      [1913 Webster]

   Baby jumper. See in the Vocabulary.

   Bounty jumper. See under Bounty.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Baby jumper \Ba"by jump`er\
   A hoop suspended by an elastic strap, in which a young child
   may be held secure while amusing itself by jumping on the
   floor.
   [1913 Webster]