Generally speaking, “proverbial” can be defined as something that is a word or phrases which references a proverb or an idiom. Some of the things described as “proverbial”, especially as used to define an entire group of people, can therefore become borderline stereotypical in nature. In more cases than none, however, “proverbial” is used amongst Biblical backgrounds, serving under the more generic term of “proverbs”. Its synonyms include that which is famed or famous, renowned, and well-known.
One common use of the word “proverbial” is to describe something that is reiterated enough times to make it viewed as essentially an adage of sorts. In this context, the word takes a particularly Biblical form, describing pieces of wisdom that are reiterated as truth. For example, the Proverbs section of the Bible could literally be considered the “proverbial” word of God.
“Proverbial” is also often used to define something that may not physically exist but the symbolism of which is important to make a point. The common example for this usage of “proverbial” would be sinking a proverbial ship. The use of “proverbial” in this expression reaffirms that the ship mentioned is not in fact a real ship while still conveying the overall message.
Most crucially, however, “proverbial” is used as a way to describe something commonly known and spoken about. For example, the expression about a “smoking gun” is one that is used commonly enough to be understood. By calling this the “proverbial smoking gun”, its cultural prevalence is also emphasized.