I knew that there would be no real definition and JU was definitely in my thoughts about this.
To me it seems like a function of effort and not really comparable between riders. Let's take spinning as an example. We all know that it's possible for one rider to be spinning the same gear as another rider is having to mash. (that's usually my problem). This means that the spinning rider is able to push that gear with little perceived effort.
As you get stronger and can make more power with the same intensity, you develop the ability to spin that gear you used to mash.
In the past I've avoided the feeling of pressure on my legs from a bigger gear and upped my cadence to maintain speed. This has worked to a point, but I know I'm weak when it comes to wind or hills. I usually get dropped unless I go really hard.
Last night I deliberately chose a harder gear and kept cadence about 80 and even less on some hills. I was trying not to blow up and just gain some leg strenght - almost like a weight workout. I ended up flying up some of the hills that used to really hurt with less perceived effort and equal or greater speed.
If I went too far overboard on the bigger gear, I got into the 50 rpm range and had to exert too much force to keep it going. In my mind, I went from pushing a big gear to mashing.
Man, this is like trying to describe the color blue!!