just a quick question, on the meaning of pip. i was told it was when the beak has pierced the air sac inside the shell. but in this site it seems defined as when the beak pokes a hole in the shell itself. in which case, i used the term incorrectly on {a social networking site} i like to brag on. if piping is cracking the shell, then what is it called when you can see the beak rupture the air sac?