What is this symbol? ⎋ (it is listed as menu shortcut)
To be concise: the symbol you're asking about, the circle with the arrow escaping from it (that's the way I remember what it means), is the Apple way of saying 'The ESC Key'.
So the menu item ⌥⌘⎋ is option+command+esc pressed simultaneously.
The Escape key.
I don't know why Apple use this non-standard symbol, but they always have...
Here is a full list of all of the symbols that Apple use.