Argot refers to the language or set of words used by a particular group of people.

// The novels were such a success that fans began communicating in the secret argot spoken by the series’ characters.

Fungible describes things, such as currency, goods, and commodities, that can be exchanged for something else of the same kind or value. In broader usage, fungible can also mean “interchangeable,” as well as “readily changeable to adapt to new situations.”

A nemesis is a formidable foe—an opponent or enemy who is very difficult to defeat. As a proper noun, Nemesis refers to the Greek goddess of vengeance.

// She will be playing against her old nemesis for the championship.

To aggrandize someone (or something) is to enhance their power, wealth, position, or reputation. Aggrandize can also mean "to increase or enlarge" or "to praise highly."

// Critics of the book argue that the author aggrandizes corrupt politicians.

Watershed, used figuratively, refers to a crucial dividing point, line, or factor. Used literally, the word may refer to a ridge from which rivers drain on either side, or to the area of land that includes a particular river or lake and all the rivers, streams, etc. that flow into it. : a crucial dividing point, line, or factor

// The protests marked a watershed in the nation’s history.

// The Continental Divide is the most well known watershed in the United States.

When we describe something, such as data, as empirical, we mean that it originated in, or was based on, observation or experience. Empirical can also be used to describe something that can be verified or disproved by observation or experiment, as in “empirical laws.”

// The team of conservation biologists has over the years collected reams of empirical data, from species inventories to soil analyses.