The tendency for certain programmers to reject new, more efficient, cleaner methods for writing code in exchange for what they perceive as doing things "their way". What this usually translates into is a buggy program with no comments, meaningless variable names, no indentation, and a monolith of if/else/switch/case statements as opposed to using an object oriented structure.
Like most shitty poetry, ego code is beautiful only to it's creator and an annoyance to everyone forced to work with it.
Guy 1: Oh my God, Linux is SO OVERRATED, nothing works for it!
Guy 2: That's because its Linus' ego code.