There are various synonyms for the term "peak relay" that can be used interchangeably depending on the context of the discussion. The term "summit shift" is an alternative to peak relay since it denotes the highest point or most elevated position in a particular niche. "Climax transmission" is yet another synonymous term that refers to the highest point in a system or process. "Apex exchange" is also an apt expression that essentially refers to the same thing- the highest point in the system. Lastly, "culmination junction" is another term that can be used to refer to peak relay in different contexts. Ultimately, the appropriate term to use depends on the specific nature of the discussion.