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

source-level debugger

    A debugger that shows the programmer the
   line or expression in the source code that resulted in a
   particular machine code instruction of a running program
   loaded in memory.  This helps the programmer to analyse a
   program's behaviour in the high-level terms like source-level
   flow control constructs, procedure calls, named
   variables, etc instead of machine instructions and memory
   locations.  Source-level debugging also makes it possible to
   step through execution a line at a time and set source-level
   breakpoints.

   In order to support source-level debugging, the program must
   be compiled with this option enabled so that extra information
   is included in the executable code to identify the
   corresponding positions in the source code.

   A symbolic debugger is one level lower - it displays symbols
   (procedure and variable names) stored in the executable but
   not individual source code lines.

   GDB is a widely used example of a source-level debugger.

   (2007-04-03)