There's a lot of weird descriptions we use in coffee for many different things. It seems to me that a lot of it for me comes down to having a similar vocabulary or else it just doesn't make sense. One of the terms our Taiwan brethren use to describe a specific point in the roast is when the proverbial sweet potato turns from starch to a 'cooked' sweetness. Only the nose knows when that is!
If that makes any sense to you, you might be quite ahead of the curve.
There are a bundle of terms that we have from 'green' astringency to 'pencil lead' bitters and of course the 'baggy' and 'bakey' from a variety of variables. It occurs to me that the bakey descriptor is a hard one to quantify as it can be anything from a full on cardboard 'generic coffee' aroma to a simple oft unnoticed dulling of aroma and fruit. My favorite though is the term 'charr.' It's what we use to describe the caramel note imparted by the perforated drum. For instance, you may bake corn in an oven vs over an open grill. The latter being our little roaster. Easy to burn and hard to cook through but the reward of getting it just right is an explosive balance of mid tones AND fruit in the same cup.
My least favorite descriptor is acidity and you won't see me use it much to describe a pleasant coffee. Acidity is really a misunderstood term so I propose we simply rethink it or at least use it more sparingly. It's just too all encompassing of the good and the bad without distinguishing either. Many strongly acidic coffees can often be attributed to either a roast byproduct(intentional or not) or a problem with the coffee. A bit green and improperly dried where the astringency is often erroneously described as acidic is something I have seen quite a bit of. When the acidity is pleasantly balanced, not a byproduct of error or defects, then I typically term it as fruit which it will often resemble. A nice cup of coffee can have ample fruit character without closing your throat or turning your stomach. A fruity cup can be juicy or jammy but it shouldn't curdle your milk!
This one particular coffee we roasted tonight is a strong Kenya. Powerful aromatics and fruit in the cup like a pleasant Lychee or Longan fruit. Something tropical and sweet but I dare not say it's acidic in the classic manner. Past roasts where a green astringency showed through after days of rest were most definitely acidic/tannic/astringent. This roast was decidedly sweet and juicy with a popping aroma which beats down the roast we did only two days earlier that we were wowing over. It has a nice acidity but it's not acid nor acidic, therefore I just call it fruit and be done with it. Maybe acidity is a dirty word in many circles but maybe we just need to understand it a little better instead of throwing a big blanket over it all with one generic term.
I really believe building a vocabulary is key to quantifying many different things. Since we had nothing to point to, no guide, we defined our own roasts in our own terms. Mostly the errors as we saw them and quantifying the resulting tastes of those errors. This must have really confused our Taiwanese friends who did a double take at our desire for less 'roast' flavor in the coffee. I mean, coffee is roasted, so all the flavor is roast but we were so tired of that dull bitter smoke that we referred to it as 'roast' flavor. A singular note that stood out from the rest of the coffee flavors that was often simply akin to hardwood smoke.
Even in espresso, I use the term bile to describe one sour and acidic to describe another because depending on which is prevalent, you may need to decrease or increase the brew temp. Quantifying things in relative terms is just a simple aid to relating and understanding what you are tasting and relating what that comes from. Be it in the roast or in the brew method, a label helps even if it sounds funny or a bit silly.