You are right, 'contrast' is kicked around alot. It is a very handy word. It is used for lens quality, mtf, image quality, content, many things. In a black and white print I think of it as how fast the image goes from black to white for a given scale in the scene. I remember when I first got started in black and white, I figured that if I had a good black and a good white in my final print, I was home free. And like you, I noticed that sometimes prints glowed and sometimes not. The amazing thing is that prints don't even need to have black or white (pure) to have that glow. A 'grey' print can take on a very nice silver quality that glows. So, what's with that?
I attribute the glow to 'local contrast' (another term that gets much use). To me this is how well the final prints resolve texture. If you were to take a good negative and print in on several papers, you would notice that some papers do this better than others. In the shadows or the bright highlights, look for details ---texture. If it is there, then you have good local contrast.
I'm not saying that the glow is in the paper. It takes a good paper to do it, maybe all papers can do it under the right conditions, I don't know. To get the glow you need a good negative and a 'high contrast' enlarging system or use contact printing. By high contrast enlarging system, I mean the total flare of the lens and the enlarger needs to be low. Or, to put it another way, the stray reflections inside the enlarger need to be minimized. It needs to be real black in there and use a good lens.
Now the negative. Probably the most important. We do a lot of zone system talk here. How much ASA or ISO, contrast, normal, etc. This is important. However, I think most everybody is underexposing their film. They have the right ISO, but the great god Ansel told us to place our shadows on zone 2.5 and so we do. We think this is the law of zones. We think this should work and once in a while it does. However, if there is any texture there, and there usually is, it will become lost. A meter reading that reads for zone 2.5 is an average (over one degree for the spot meter folks). That means that some of the reading is less and some more. On the film, anything short of the 2.5 will have no local contrast (just like the paper). The film curve is just starting to tip up and gain contrast at this point. It just won't separate the fine detail. It will be mushy and mush doesn't glow. Mush has no detail, no local contrast. At the highlight end of the scale, same problem. Some film/developer combos have a maximum density. Above this, more exposure gives no more density. So if there is are little fine details sparkles in something, like wet grass in the sun, those little sparkles are going to be dull. They just don't hold the detail.
What is the solution to all of this? On the shadows end, the exposure end, it is plenty of light. I don't usually worry about zone 2.5 at all. I am measuring what I think is zone 4. This is usually where the image is more important for me and the negative is really starting to develop some local contrast (getting out of the toe of the film curve). When I'm in doubt, I overexpose by a stop. With large format, this doesn't matter. Largeformatters are usually not worried about grain. With smaller format, do it if you can. Better to glow and be grainy that the other way around. Grain free muddy prints don't get shown. With a well exposed negative, you can burn down the zone 4s to zone 2 and there will be a wonderful quality about them. Dark, yet full of detail that implies light to your brain.
On the highlights end of things, one needs to pick a film/developer combo that works for them. I would say a compensating developer and a film with a long shoulder. If you don't do this and you do overexpose, then your negatives will block up and that is bad. A blocked negative means the density of highlights in your negative will all be the same and highlight texture will be gone. It's not good to overdevelop, but with the right combo of film/dev, it is not as critical as when you risk blocked highlights.
There is another glow you see in some artist's prints. Either through lighting or the 'hand-of-god', there is something about the print that is abnormally lighter than it should be. Small amounts of this go undetected, but sometimes it is so strong that it is easily detected as a bad dodge/burn. It is when it is right on the brink that something appears to glow. This is a matter of style and not one of my favorites.
Now before you all roast me for this, let me say this is only my opinion and that it has worked for me. Your mileage may vary. If this gets the discussion going, that is a good thing. I'd like to put a glowing print up in the apug gallery, but I just got a scanner and I don't think I could get it to glow on a monitor.
Best of luck.