A single pad ramming, or maybe a couple in a row might be a player trying to learn how to fly. Some are awful, in fact once I ... being kind of distracted due to a teenager crisis behind me... crashed into PO and my ship stuck into the lobby.
To me, griefing in a PVP game is more about how you play. If you play to deny other players the ability to play you're probably a griefer. That would include camping, but camping can be regular game play too. The difference is the amount of chance you give to other players - do they have a way out other than not playing the game? CIG needs to define this.
The most interesting anti-griefing I ever saw was implemented by Linden Labs in the game Second Life. You got banned... which did not mean you could not play. But when you logged in, you found yourself in a field of grass. That could persist for a number of days. Enough in a row they just cancelled your account and you had to appeal to get the account back. Eventually they let players manage most of this and only intervene if an real life law was broken, or it cost someone real money.
Intent is the key. If someone rams a ship or two at a pad at PO and apologizes for it, that's one thing. If they keep doing it, I would probably heartily and politely suggest they go learn to fly in Arena Commander.
If they hit a single ship and then start bragging about what they did in chat, that person's a griefer.
A person who shoots you dead as you lower the ramp or elevator on your ship so they can steal it...that's a pirate. I might hate it, but it's legitimate gameplay.
A person who forces their way onto your ship at a major port so you have to sit in the pilot seat and watch Netflix until the ship despawns due to inactivity because they refuse to leave is a griefer because there is no legitimate gameplay loop to remove them. Even if you do move out of the armistice zone, they will shoot you in the pilot's chair as soon as you leave it.
Someone tries that at a non-armistice zone and you shoot at them or they shoot at you. Again, legitimate gameplay. It's splitting hairs, but when rules prevent you from defending your own stuff and someone uses those rules to put themselves at a distinct advantage, then that's griefing.
Someone sitting outside an armistice zone with long range weapons threatening to destroy ships in the zone if they don't put up an escort tag are the same. Sit in an area where you are both exposed? Legit gameplay in my mind....even if you shoot at them while they are running to their ship. Sit where the person can't fight back? Griefer. Again, those are my personal definitions. Others may think differently and that's ok. The only thing that my definition means is I won't help that player again. If they ask a question, if they ask for help, it's a big silence from me. Let them get someone else to help them.