If someone says something in a stage whisper, they say it as if they are speaking privately to one person, although it is actually loud enough to be heard by other people
a loud whisper that can be overheard; on the stage it is heard by the audience but it supposed to be inaudible to the rest of the cast
The captain's voice, by G–!” said the stage-whispering ruffian, and both robbers fled by the way of the back door, shutting off their bull's-eye as they ran.