WordNet (r) 3.0 (2006):

symbolic logic
    n 1: any logical system that abstracts the form of statements
         away from their content in order to establish abstract
         criteria of consistency and validity [syn: symbolic
         logic, mathematical logic, formal logic]

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

symbolic logic

    The discipline that treats formal logic by means of
   a formalised artificial language or symbolic calculus, whose
   purpose is to avoid the ambiguities and logical inadequacies
   of natural language.

   (1995-12-24)