This is a strange definition of 'buggy' to me. Surely it shouldn't depend on anything to do with the source code, otherwise closed-source programs are all 'neither-buggy-nor-not-buggy' and that can't be the case...
Most software is incapable of being incorrect, because correct behavior isn’t defined! Hence the questions here about who’s to say what’s correct. When the typical programmer says a program is “buggy” it means “it didn’t do what I want.” That’s a pleasantness property, not a correctness one.