duplicate post - should have looked through page 1 first.
To me a beater is an expendable commodity guitar that can easily be replaced in kind for minimal $$$.
I have a nice old Seagull M6 (precursor to the S6, with laminated mahogany and cedar top). It has been on many flights, guitar camps, the back of motorcycles on long trips, and some iffy situations where the expensive ones just don't go. This one is nearly 30 years old and it's been mine for most of its life. Come to think of it, it would be a real shame if anything happened to it, so maybe it isn't a "beater" any more.