The Collaborative International Dictionary of English v.0.48:

Dumpy level \Dump"y lev"el\ (Surv.)
   A level having a short telescope (hence its name) rigidly
   fixed to a table capable only of rotatory movement in a
   horizontal plane. The telescope is usually an inverting one.
   It is sometimes called the Troughton level, from the name
   of the inventor, and a variety improved by one Gavatt is
   known as the Gavatt level.
   [Webster 1913 Suppl.]