This phrase literally means “blind fist defeats the master” and basically means beginner’s luck. In Chinese kung fu, there are a variety of different styles from mantis fist, tai chi and drunken style, but despite the popularity of this phrase, there is no such style known as “blind fist”. Presumably, one would not be advised to practice blind fist, especially against opponents who can see.
However, Everybody knows of an amateur who tries his hand at a game for the very first time and ends up beating a group of seasoned experts despite flailing about like a blind man in a dojo. When you come across this kind of injustice, you’ll understand the true meaning of 盲拳打死老師傅