I think you are the one not understanding...
I already posted "Stalk" definition...
here is another definition...
No matter the kind of mental gymnastic you use, the fact that Hinata falls into this definition (and the other one too) still remains
You are exaggerating what stalk means, stalk is the simple act of following someone or observing them persistently or for a long time, being this the case, what Hinata's character did completely fits.
....
Again, you do NOT understand what it means to stalk or to be a stalker.
If you want to rely so much on a single definition to make your case, here, let's play with those. From the United States Department of Justice: http://www.justice.gov/ovw/stalking
Stalking is a pattern of repeated and unwanted attention, harassment, contact, or any other course of conduct directed at a specific person that would cause a reasonable person to feel fear.
Stalking can include:
Repeated, unwanted, intrusive, and frightening communications from the perpetrator by phone, mail, and/or email.
Repeatedly leaving or sending victim unwanted items, presents, or flowers.
Following or laying in wait for the victim at places such as home, school, work, or recreation place.
Making direct or indirect threats to harm the victim, the victim's children, relatives, friends, or pets.
Damaging or threatening to damage the victim's property.
Harassing victim through the internet.
Posting information or spreading rumors about the victim on the internet, in a public place, or by word of mouth.
Obtaining personal information about the victim by accessing public records, using internet search services, hiring private investigators, going through the victim's garbage, following the victim, contacting victim's friends, family work, or neighbors, etc.
Source: Stalking Resource Center, National Center for Victims of Crime
This is what it means to stalk and to be a stalker, hence why I have repeatedly said calling Hinata one is insane. At worst, her actions are consistent with someone who is painfully shy and has little self-esteem. Seriously, look up sites that talk about shy people and their behaviors. Those would be far more accurate than OMG!STALKER!! I should know because, yes, I am one of the shy people they're describing, and I'm reasonably certain I'm not a stalker. To really fall into that category, there has to be a certain kind of intent involved, as well as multiple acts, because I can't think of any known stalker that only does one thing -- they're known for several brands of debilitating and increasingly dangerous behavior.
Now consider these points:
+Naruto asking Sakura out is not harassment, it's harassment if she denies and he still insists on it
Naruot has repeatedly aske Sakura out on dates, as well as insist upon them being an item, to which, Sakura has swiftly and decidedly rejected him, either via the word No, or with physical violence. That's harrassment.
+She specially observed him while he was training, so it would make sense that the main characteristic she took a real grasp was the never give up attitude, it doesn't make her any less of a stalker because she actively did spy and observed Naruto without his consent
So, if I were to happen upon someone doing exercise and watched them without saying anything for a few moments, does that automatically mean I'm a stalker? Or for the matter, is it stalking if you happen upon a scene that captures your attention?
+The story not only hints that Hinata consistently spied and observed Naruto, there is also no evidence to prove that she didn't stalk him.
First, that makes no sense. If Hinata wasn't constantly spying on Naruto, of course there would be no evidence. Also, given the success ratio of relying on "hints," I would not go relying on those exclusively to determine someone's activities. If anything, Hinata has approached Naruto directly at the hospital when he was hurt, only to faint at the sight of his heavily bandaged form, and as a result, could not bring herself to face him due to shame.
It sucks to be a shy person, believe that.
+You are trying to argue the it's only "stalking" IF Hinata knew everything about Naruto, no it's not, she follows and observes him without his consent, like a spy be it for her shyness of for whatever motive it is it still is stalking
Again, stalking and being a stalker comes with a whole nother bag of gravity than looking at/admiring someone. If you want to insist that any activity of looking at someone without conversation or granted consent is considered stalking, you might as well start jailing most of the population, because we've all done it at some point.
+Her confession isn't really mind blowing tbh, she was selfish over there, like rocci said, a YOLO moment, she was afraid of Naruto dying without knowing her feelings and thus she went there to simply confess, she didn't have a plan to save him or anything like the Anime tried to put it. What is mind blowing is that Kishi chose to ignore and retcon what happened during that scene with the Last in a reallypathetic manner.
Hinata admitted to being selfish, yes, that's true. However, calling it a YOLO moment, or her trying to score a few brownie points is asinine, demeaning, and hugely disrespectful.
In order for Hinata to live the path that she had chosen to live, there was no other recourse for her but to go forward and defend Naruto to the death. To have played it safe, sure she would have lived, but she would forever beat herself up for not doing something, anything, even in the face of dying. It's roughly the same thing Naruto has done on several occasions, from the time that he made his pledge after the Demon Brothers skirmish to confronting Zabuza, taking on Neji, defending Tsunade from Kabuto, among others. It was her taking responsibility as a human being to care for and defend her fellow man, even when no one else is willing to step forward, thereby overcoming the Bystander Effect that makes things "not my deal." She didn't have a plan to free Naruto because she could only depend on herself to do what was true to herself and the way of life she decided to uphold, hence, her standing her ground against Pain, totally prepared to die in belief of her ideals.
As I said you can try to bring up the fact that she was not shown actively stalking or whatever, but not only does there is no proof that she didn't, there is also hints in the manga that she indeed made a habit out of observing Naruto's training sessions.
There is also the fact that we never saw much of her life because she was not relevant, with the limited grasp of what we have in what Hianta did, it's pretty safe to say that her actions regarding Naruto were within what the definition of "stalk" means.
The closest it comes to hinting Hinata admired Naruto often when when Sakura commented on their time in the Academy. After that, we have Kurenai's flashbacks of Hinata training hard to not be a failure, while still screwing up missions. If anything, it's pretty easy to say Hinata didn't have time to sneak-sneak-sneak, if she was ever involved in it in the first place; she had her own fish to fry, and Kurenai seems to be pretty well-informed about that, since it's her own student.
Persona 5 hype 
