Not single word answers but within the non-commissioned ranks you would talk of someone "losing a stripe" or "losing his stripes" and I have even heard of someone loosinglosing a pip when reduced in rank within the lower commissioned ranks.
For someone who committed a serious enough offence to looselose their commission without simply being either jailed or dishonourably discharged, (a delicate balancing act), they would be "stripped of their commission" -- note that this is not the same as being decommissioned. Or, if busted all the way back to private, "stripped of all rank".
I think I can remember a case or two in the history books where an officer was stripped of all rank before being hung or shot usually for cowardice, either because 1 officer stripped of commission and 1 enlisted man shot is better in the reports than an officer shot, or to add ignominy to the punishment.
Finally we get to the single word answer cashiered - i.e. stripped of all rank or position due to some misconduct but with the additional connotations of a ritual humiliation thrown it.