I'm just waiting for the amateur psychologist descriptions from certain members
Let that be me then.
As someone pointed out, griefing is defined as "A griefer is a player in a multiplayer video game who deliberately irritates and harasses other players within the game, using aspects of the game in unintended ways." (Wikipedia) so let us break down what this means.
The first part states that to be a griefer, you must -deliberately- irritate and harass people. That is obvious. The second part "Using aspects of the game in unintended ways" is I believe the most important part.
For example: In Call of Duty the aim of the game is to kill people, so if someone keeps killing you and you do not like it, well that is not grieifing as it is using aspects of the game in intended ways.
When people here say they are being griefed because they keep getting killed, one says "Well this is GTA, of course they should expect to be killed" which at first glance makes logical sense and would put this game under the same list as Call of Duty. However let us look back at the second part of the definition again: "Using aspects of the game in unintended ways". I bolded a part of the definition that I wanted to stand out. What does unintended me, as in who does it relate to? Do the players define what is unintended? Well if that was the case if you asked 10 people the intended way of playing GTA you would have 11 answers.
I prefer to go by what the developers intended and to find out what they wanted GTA to be let us look no further than the GTA Online trailer. In the trailer you had a focus on cooperative aspects and PvP was rarely used and only in justifiable circumstances. That is what the GTA devs wanted, not this slaughter fest.
So if a player is deliberately irritating and harassing you by spawn camping you, well that would be grieifing.
I must be an a short essay mood, this is my second one today