From The Jargon File (version 4.4.7, 29 Dec 2003) :
prettyprint
/prit'ee?print/, v.
(alt.: pretty-print)
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.