A mcdojo is a commercially-oriented martial arts school. The term comes from a meld of 'dojo', the Japanese word for 'school', and 'McDonald's', the ever-present icon of commercialism.
Schools deserving of this derogatory term are ones that are concerned with taking your money, giving you a colorful new belt, and pushing frivolous merchandise.
Typical signs of a mcdojo:
- a majority of the high-ranking students are children
- high-ranking students are out of shape (this shows a lack of standards; students are passing tests regardless of actual skill and fitness)
- contracts and periodical mandatory expenses
I advise anyone interested in practicing martial arts to be very thorough in judging schools. Make sure that the teachers are credible. Ask about the grading standards (there should not be a 100% passing trend). Most of all, be sure that you'll actually learn something instead of just doing loads of push-ups and being handed a new belt every few months.