Richard Pennycuick asks:

>No, not the label, but the word, as in Op 14 bis.  I haven't been able
>to track down any reference to this, but by finding a few examples of its
>use, ...

Normally, it means to repeat notes or measures or even entire pieces.
The Harvard Dictionary of Music gives this definition, but not what "op.
24 bis" means.

What a gyp!  Has Harvard gone to hell?

Steve Schwartz