The Collaborative International Dictionary of English v.0.48:

Symbal \Sym"bal\, n.
   See Cimbal. [Obs.]
   [1913 Webster]

The Free On-line Dictionary of Computing (30 December 2018):

SYMBAL

   SYMbolic ALgebra.  A symbolic mathematics language with
   ALGOL-like syntax by Max Engeli, late 60's.  Implemented for
   CDC 6600.

   ["User's Manual for the Formula Manipulation Language SYMBAL",
   M. Engeli, TRM-8.00, Comp Ctr UT Austin, June 1968].