Mill: It’s a verb! It’s a noun! NO! Or rather, yes... Both? it’s complicated.
Before diving too deep into milling history let us first take a look at how mills were defined, both today and in our historical period. Depending on whom you ask the term “Mill” has a multitude of meanings. To an architectural historian it may be an industrial building or complex. To a machinist it’s a verb referring to cutting down or working a piece of metal. To a welder it could be a place where steel and other metals are made. Let’s take a look at what dictionaries, both modern and historical, have to say on the subject.
Today, Webster’s dictionary gives nine definitions of the term as a noun, ranging from the building, or complex of buildings, housing the equipment to perform an industrial process, to an automobile or boat engine. It provides three definitions for the term as a verb, and an additional three as an intransitive verb; these range from mechanical operations such as cutting, grinding, or shaping, to wandering around aimlessly (milling about). If there’s this much ambiguity about the meaning of the term today, how was it defined historically?
The 1728 edition of Ephraim Chambers’ Cyclopaedia: or, An Universal Dictionary of Arts and Sciences provides the following definition: “in propriety a Machine used for Grinding. But the word in its more general Signification is used for all Machines whose Actions depend on circular Motion.” Moving forward through the 18th century, the 1760 edition of John Marchant’s A New Complete English Dictionary provides this definition: “a machine or engine for grinding corn, and for various other purposes; of which there are different kinds, according to the various methods of applying the moving power: as water mills, wind mills, mills worked by horses &c…” At first, both of these entries suggest that the 18th century definition was significantly simpler than the modern. But that may be misleading, so let’s look deeper into how the term was actually used.
Marchant’s work gives more insight into how the term was used in the 18th century. In the period the term “mill” seems to have generally referred to a machine used for grinding corn (grain) but would have likely been even more accurately defined with modifiers such as “water mills, wind mills, mills worked by horses &c…”  So perhaps, then, it makes more sense to look into how Newlin Grist Mill itself would have been defined.
There are two ways we could approach this: power source or product.
Power Source: We use an overshot (the water runs over the wheel, rather than under it) waterwheel, fed by the fall of a mill race. Using Chambers’ definition this would make us a water-mill , as opposed to a windmill (one powered by wind), horsemill (one turned by horses), or human-powered mills.
Product: Many mills were referred to by their product or process. Chambers describes fulling, leather, forge, linen, and gunpowder, to name just a few.  At Newlin we grind grain into meal or flour. So naturally we should be a grain mill, or maybe a flour mill? Or a meal mill? But these terms don’t show up in the historical record. Instead, either “grist mill” or “corn mill” seem to be the operative terms for a mill which grinds grain (it’s worth noting that “corn” in this period refers to any grain, not just the corn we have in North America today). But neither of these terms get explicitly defined but dictionaries; rather, they show up in other works, and their meaning is only discerned by context.
In conclusion, what does “mill” mean? Many different things. But in our historical period, it mostly referred to machines used for grinding or whose power came from some form of circular motion. How would Newlin Grist Mill be described in the period? This is more difficult to answer. It’s certainly a water-mill. But aside from that we don’t have a strong definition which fits our mill well. So perhaps water-mill, gristmill, or cornmill would all be correct?
These questions are what make research into this period so fascinating. Learning how people describe an object or place gives us a brief glimpse into their world and mannerisms. So while I apologize for not giving you a hard and true answer, I ask you, instead, to find a term which you use often but which might not show up in a published dictionary. Feel free to leave your term in the comments below.
 Merriam Webster, Incorporated. 2019. Mill Definition of Mill by Merriam Webster Dictionary. https://www.merriam-webster.com/dictionary/mill?src=search-dict-box
 Chambers, Ephraim. 1728. Cyclopaedia: or, An Universal Dictionary of Arts and Sciences. London. https://archive.org/details/Cyclopediachambers-Volume2/page/n197 Pg. 551
 Marchant, John. 1760. A new complete English dictionary. London: J. Fuller. https://babel.hathitrust.org/cgi/pt?id=njp.32101037601679&view=1up&seq=534. Pg. 535
 Chambers, Ephraim. 1728. Cyclopaedia: or, An Universal Dictionary of Arts and Sciences Pg. 551
Chambers, Ephraim. 1728. Cyclopaedia: or, An Universal Dictionary of Arts and Sciences. London. https://archive.org/details/Cyclopediachambers-Volume2/page/n197.
Marchant, John. 1760. A new complete English dictionary. London: J. Fuller. https://babel.hathitrust.org/cgi/pt?id=njp.32101037601679&view=1up&seq=534.
Merriam Webster, Incorporated. 2019. Mill Definition of Mill by Merriam Webster Dictionary. Accessed Aug 05, 2019. https://www.merriam-webster.com/dictionary/mill?src=search-dict-box.