I never really knew that this meant until I switched industries and joined the legal field. At my firm, I am a square peg in a round hole. I am surrounded by a ton of really, really smart lawyers and people who have been at the firm for decades and don't know anything but the legal field. Even the majority of our management has exclusively worked in the legal industry and doesn't know anything different. These are also people that exclusively think in one direction. I don't think that this is wrong by any means. This is the round hole.
I am the square peg. I am very different from everyone I work with. Let's start with appearances. I dress completely different from most of them. They have a uniform they each wear and it is some combination of the same style shirt, pants, and shoes every day. Often in neutral colors. Me? I am don't wear the same thing twice in one month. I wear bright colors and animal prints. I change my bag every day. My casual wear is more eclectic and dressier than most of their everyday outfits. I laugh loud. I love to talk to people about all kinds of things. I love to joke around - even while doing work. I am viciously creative. I feel like I am in an environment when creativity is not welcome and change is so scary that it is easier to justify not changing. That is the (round) box that I work in and I show up everyday as my (not at all) square self.
Don't get me wrong, this is not a criticism. Just an observation. The round hole is super successful and there is nothing wrong with the way they chose to live.