Utilitronium is relatively homogeneous matter optimized for maximum utility (like computronium is optimized for maximum computing power). For a paperclip maximizer, utilitronium is paperclips. For more complex values, no homogeneous organization of matter will have optimal utility.

Utilitronium shockwave is a process of converting all matter in the universe into utilitronium as quickly as possible, which would look like a shockwave of utilitronium spreading outwards from the point of origin, presumably nearly at the speed of light.

See also

Utility function
Hedon, Utils
Paperclip maximizer, Complexity of value
Hedonium, the hedonistic utilitarian version of utilitronium