Similar to the word homo, however a zomo need not be truly homosexual nor "gay" in the non-literal sense. A zomo simply moves along like a zombie doing whatever everyone else does. Zomos love music, movies and styles of clothing that are completely mainstream. A zomo is a true plebeian example of American 21st century culture. A zomo can belong to any subculture, so there can be jock zomos or emo zomos etc...
All that is needed for a zomo is complete mental domination by the media.
Joey: "OMG I can't wait to watch American Idol tonight!"
Mike: "You are so Zomo."