A Korean bird, called Crow tit in English. There is a common idiom/ saying : "the crow tit
will break it's legs trying to walk like a stork". Other translations include try-
hard and
poser. Basically trying to be something that your not.
BTS refers to themselves as baepsae because they are not part of a big name entertainment company and they are still becoming international idol stars. They are proud to be baepsae.