What does 
mean on Mac?
What does mean on Mac? A prohibitory symbol, which looks like a circle with a line or slash through it, means that your startup disk contains a Mac operating system, but it’s not a version or build of macOS that your Mac can use.
A prohibitory symbol, which looks like a circle with a line or slash through it, means that your startup disk contains a Mac operating system, but it’s not a version or build of macOS that your Mac can use.
