Terrible Cluster of PIs

When we first saw [Ajlitt’s] Hackaday.io project Terrible Cluster we thought, perhaps, he meant terrible in the sense of the third definition: 3. exciting terror, awe, or great fear; dreadful; awful. (Dictionary.com) After looking at the subtitle, though, we realized he just meant terrible. The subtitle, by the way, is: 5 Raspberry PI...