The Collaborative International Dictionary of English v.0.48:
Jump \Jump\, v. t.
1. To pass over by means of a spring or leap; to overleap;
as, to jump a stream.
2. To cause to jump; as, he jumped his horse across the
3. To expose to danger; to risk; to hazard. [Obs.]
To jump a body with a dangerous physic. --Shak.
(a) To join by a butt weld.
(b) To thicken or enlarge by endwise blows; to upset.
5. (Quarrying) To bore with a jumper.
To jump a claim, to enter upon and take possession of land
to which another has acquired a claim by prior entry and
occupation. [Western U. S. & Australia] See Claim, n.,
To jump one's bail, to abscond while at liberty under bail
bonds. [Slang, U. S.]
To jump the gun, to begin to run (in a footrace) before the
starting gun has fired; hence, (fig.) to begin any
activity before the designated starting time.
[1913 Webster +PJC]