They are using a dictionary definition, I believe. It is “Engineering of Chaos”, which is to describe how computer systems, especially when distributed, can ha

They are using a dictionary definition, I believe. It is “Engineering of Chaos”, which is to describe how computer systems, especially when distributed, can have near random failure states, resulting in what appears to be a chaotic system. Network partitioning, hard drives failing, bits randomly flipping because of physics would all be examples of such failure states. The engineering comes in when we try to simulate such situations and create processes for hardening applications against those types of failure.