In the sense of a person that "breaks the mold"? A person that "breaks the mold" is somebody who does things differently or in a way that is unexpected. For example, an accountant that "breaks the mold" would be extremely extroverted and go out to parties every evening. The general stereotype or "mold" of accountants is that they are introverted, quiet and kind of "geeky" if that makes sense. Hope that helps. Cheers.

On the origin of the idiom (you might find it helpful): a mold, or casting mold, is used to make metal tools or art. For example, if I want to make a metal sculpture, I will first carve the opposite image into a material that won't melt, such as plaster (like cement). Then I'll pour in the molten (liquid, hot) metal, and wait for it to dry. Then I break the mold, and I have my sculpture, as a mirror image of its opposite. This is in contrast to some forms of metalworking, where the mold is made of something that will not melt (for example, making art out of gold, but using an iron mold). With this method, you can make the same thing, without breaking the casting mold, again and again and again... so it can be seen as monotonous. So: in breaking the mold, I have done something that cannot be repeated or changed (literally), because the casting mold is gone. Figuratively, I have changed the way that things are done, or changed things in a radical way. Basically to do things in a very different, new way. Last note: "to break the mold" usually has a positive, rather than a negative, meaning.