Having a machine do something a person did. The word hides an important distinction: automating a task is not the same as automating a job, and most jobs are bundles of many tasks. It also hides a second one, between automation that removes the person and automation that changes what the person spends their time on.
Technical view
Literature on levels of automation runs from advisory through to full autonomy with no human involvement, and the middle levels are where most difficulty lives, because partial automation creates monitoring roles that people perform badly. Related concepts include the irony of automation, that automating the easy parts leaves humans with only the hard residual, and automation-induced complacency. These findings predate AI by decades and transfer directly.
Related
Part of AI Terminology Index, section: The Foundations.