I only recently came across the use of the term "grind" in an RPG context. I know, I know-- I am an out of touch grognard who is prone to telling modern gamers to get the hell off my lawn. And I certainly have no excuse, since both my wife and several of my best friends are complete Warcraft fanatics. So I should have known about this phenomenon, but didn't. To my understanding, a "grind" is a situation where you're just engaged in melee after melee, stacking up x.p. Hardly the epitome of role-playing, of any style.
It got me thinking, though, about the applicability of the grind in an old-school dungeon crawl. I mean, my own Castle of the Mad Archmage could, if played that way, be considered a grind. There are tons of monsters, often in rooms not too far removed from one another. Certainly I don't use the "20% of rooms in a dungeon should have monsters" rule of thumb that the earliest versions of the game proposed. At best, I invert it.
But I must say, a grind is how you play it. It's a matter of attitude. Both the attitude of the players to the ultimate goal of entering a dungeon, and of the game master to the ultimate goal of having players enter the dungeon in the first place.
I think that the "old school" approach to dungeon exploration is not to clear the level and then move down to the next. At least, as it applies to the megadungeon; certainly smaller dungeons might well be designed with the ultimate objective to be "wipe out all the goblins who are raiding the halfling village". But in the old school approach, you're not out to kill the monsters. You're out the get their treasure. In the old school approach, a plethora of monsters might actually be considered a boon. There's a tribe of orcs a few corridors away from a derro outpost? The "grind" mentality would say, take out the orcs, then move on to the derro. The old-school mentality would say, get the orcs to fight the derro through clever play, and take their chest of gold while they're busy hacking each other to bits.
So I think that any grind you can come up with, short of something that was just one room after another, completely linear, stuffed with monsters, the old school could turn into a tactical challenge. That's why there are all those seemingly useless corridors; flanking! And there's no stat check for strategy.