What is Employee Engagement? Do you know?

Employee Engagement is one of the most monitored and discussed human capital metrics today.  We are told that in order to be a strategic partner to the organization, we need to engage our employees.  However, what does that really mean?  We throw countless hours and dollars at the concept of employee engagement, but do we even know what we are measuring.  Have you ever seen an organization that truly has won this battle and has an engaged workforce, or are we all still fighting the battle?