Unreadable or indecipherable. Something of sufficient complexity that it is incomprehensible. Often applied to someone else's style of writing software. Example: I've spent an hour trying to figure out what your freaking write-only PERL script does: lean to use some comments for a change!
WRITE-ONLY
Meaning of WRITE-ONLY in English
Slang English vocab. Английский сленговый словарь. 2012