"Marinade" is one of those words that's been stretched a lot and has come to have an expanded and pretty loose meaning. It used to require an "acid," but I don't think it still does. Some people argue that the purpose of the acid and of marinating in general was to tenderize the meat, but that doesn't seem particularly convincing. The pH differential you get from acid in a marinade acts to "power" diffusion and to more effectively distribute flavor, including better penetration
When it comes to definition, usage overtakes convention and becomes the new convention. That's just how languages -- English especially -- work. Knowing exactly where to draw the line as language evolves is impossible. Cooking is a practical art. So, as we come to understand new spins on old words those quickly cease to be spin and just get folded into the melange. On the other hand, we shouldn't be so eager that words lose all meaning and two very different things become the same.
Chris's oil, garlic and herb technique sounds like a marinade to me. And "dry marinades" are certainly popular enough that if I tell you marinate something by dry-rubbing it, covering it and holding it in the fridge overnight it shouldn't excite a great deal of comment.
I almost always use one sort of marinade or another with red meat. Most often it's a minimal amount of Worcestershire and red wine in equal proportions while the meat tempers (if that long), followed by a dry rub. The Worcestershire and wine mix with the meat juices and coagulate into something very syrupy which not only tastes good but helps glue the rub to the meat. Since I use very little, there's no need to wipe the meat before rubbing it. And with the rub applied, the meat is more than dry enough to properly sear and crust.
Finally and FWIW, the "shepherd's pie" thing between Ishbel and me wasn't about either of being right. Rather it was a way for two people, one from the UK and the other from the US, who not only both love the language but each like another sufficently to play "full contact." I respect her literacy, her cooking and everything else about her greatly. If it seemed otherwise... my bad.
In fact, we were both undoubtedly correct. Her more highly defined usage is a little more restricted to one part of the Isles, but certainly valid.
I give you a toast, ladies and gentlemen.
I give you a toast, ladies and gentlemen.
May this fair dear land we love so well
In dignity and freedom dwell.
Though worlds may change and go awry
While there is still one voice to cry
There'll always be an England
While there's a country lane,
Wherever there's a cottage small
Beside a field of grain.
There'll always be an England
While there's a busy street,
Wherever there's a turning wheel,
A million marching feet.
Red, white and blue; what does it mean to you?
Surely you're proud, shout it aloud,
"Britons, awake!"
The empire too, we can depend on you.
Freedom remains. These are the chains
Nothing can break.
There'll always be an England,
And England shall be free
If England means as much to you
As England means to me.
BDL