Yeah - I used griefer, because no-one is going to be "pirating" people who aren't carrying cargo, and it certainly wouldn't be someone interested in a fair fight, because virtually all serious explorers are unarmed.
Basically anyone doing this would be doing it purely to ruin someone's week after they had spent a long time exploring and travelling and collecting system data that they have no physical way to sell. The only challenge in it is finding the target, and if that's their goal then they can just explore in open and hail someone after meeting them.
No - the only term for someone who would actually go this far out of their way to deliberately target a helpless target for no gain to themselves and a potential colossal loss for their target (all lost exploration data) would be "griefer".
-- Pete.
Edit: To clarify, I do not think all PvP is "griefing" - only PvP where there is no expectation for the target to be able to defend themselves, no consequences for the attacker, no meaningful gain for the attacker, and severe loss for the target. Basically where the action is done purely to cause the opponent "grief" and nothing else.
In inhabited space there are bounties, there are other players, there are stations where people can run towards to be safe, people can be expected to have saved recently and had a chance to cash in bounties and exploration data etc. Players can possibly be carrying bigger weaponry or defence than expected, etc etc. This is absolutely not the case in the scenario I described in the original post.