Other forms: broke the mold; breaks the mold; breaking the mold
When you break the mold, you do something in a completely new or original way that no one else has done before. The idiom implies that something is so unique that it can't be compared to anything else.
The phrase break the mold is used in reference to an individual or achievement that is like no other. A teacher who breaks the mold teaches in an innovative and unconventional way. A writer who breaks the mold produces something entirely original. The phrase originates from the process of casting metal; if a mold is broken after a single use, it's impossible to create an exact replica. Consequently, the phrase is also used to mean that someone is one of a kind: "Once they made him, they broke the mold."