What is the meaning of square peg in a round hole?

If you are working for an organization, and you say that you feel like a square peg in a round hole, what you mean is that you fell like a total misfit. You and the others around you sense that you don’t belong there. The expression cal also be used to refer to someone who is unsuited for the type of job that he / she is actually doing.

There is a round hole. What would happen if someone inserts a square peg (which means wooden stick in square shape) into the round hole. The square peg would not enter into the hole. Because of mismatch between the two sizes. This expression is just the figurative meaning of this mismatch.

I’ve always felt like a square peg in a round hole in this university. I think it’s about time I resigned.