When you paint your descriptions in broad enough strokes, anything can be defined as a grind. And if you paint your descriptions with narrow enough strokes, anything can be defined as "not grind". In other words, whether something is a grind or not is based purely on how you word your opinion. It's word play and nothing else.
Example:
"Skyrim is a grind. Every single mission is 'go here, kill/get/deliver something'. There is nothing else to do in Skyrim."
See how I worded that? My very word choice just made Skyrim sound like a grind.
An opposite example:
"Elite is not a grind. Last night I went to a RES where there was a HUGE number of police, including a police Anaconda, and we all ganged up on a bunch of Pirate dropships who were harassing a Harmless T9 just going about his business. Then I went to another RES where there was only like 4 police and I had the fight of my life against a wing of Vipers."
See again? I just used different words, and made Elite out to sound like those were two completely different encounters, when in reality they were actually very similar.
(note: no games were harmed in the production of this post. I don't personally feel like either of these games is a grind in my own opinion.)