As a sysadmin for a government department for the last two years, I have come to the conclusion that 'Enterprise Software' actually means 'multiply the price by ten and remove the installation manual'.
I realise this response will be taken as Gen-X-hip-cynicism by some readers, but after looking at the contracts some departments have signed and the monies paid for Enterprise Software, I hope that there were kickbacks involved because I don't want to believe that anyone could be that foolish.
My personal 'enterprise level requirements' are software that is easy to install and doesn't crash more that once per month.
Actually, thinking about it a little more, enterprise level software might be 'software that you can install in under two weeks, and that takes longer to crash than the minister takes to get bored with it'.
I didn't believe in evil until I dated it.