1. To generate ?pretty? human-readable output from a hairy internal
representation; esp. used for the process of grinding (sense 1) program
code, and most esp. for LISP code.
2. To format in some particularly slick and nontrivial way.
The Free On-line Dictionary of Computing (30 December 2018):
/prit'ee-print/ (Or "pretty-print") To generate "pretty"
human-readable output from a hairy internal representation;
especially used for the process of grinding program code.