Forbidden minor is a musical term that describes a specific chord progression. However, there are several other terms that are used interchangeably with this term. One such synonym is "prohibited progression," which describes the same chord sequence that leads to an unresolved and unstable feeling in music. Another synonym for forbidden minor is "vexation progression," which specifically refers to the feeling of tension and discomfort that arises from hearing a forbidden minor chord. Finally, "illegal progression" is another term that is sometimes used to describe the same chord sequence, as it suggests that the use of the forbidden minor chord is against the rules of traditional music theory.