The term "most quadragenarian" refers to someone who is in their 40s and considered to be the most prominent in a particular group or category. Some synonyms for this phrase can include "leading 40-something," "foremost middle-aged," "top-ranking fortysomething," and "preeminent forty-plus." These terms can be useful for describing individuals who have achieved a high level of success in their careers or other pursuits, or who are considered to be notable figures in their community or industry. While these phrases all convey a similar meaning to "most quadragenarian," they provide a slightly different nuance that can be tailored to the specific context in which they are being used.