Description of the "Use of undefined constant" error.
"This is a common notice / warning that occurs whenever PHP has detected the usage of an undefined constant. In case you didn’t already know, a constant is a simple value that cannot change during the execution of a script. i.e. If you define constant A as “123”, you won’t be able to change it to “456” at a later stage."
Most likely something to do with the database you are trying to dump.