The term gekokujou refers to retainers supplanting their lords, and other situations where someone who is inferior in a hierarchy ends up above someone who was superior.
As a BL slang, gekokujou refers to a scenario where someone lower in a hierarchy is the seme, e.g. the retainer is the seme and the lord is the uke, or the employee is the seme and his boss is the uke, etc.
