In law, what does "directed at specific person" mean? Such as in harassment, an act must be directed at specific person. Does that mean they are sent it by email, phone, talking to them directly, etc? Or can it include a posting made about them--where their name is not mentioned--on your own personal blog that they search out on their own and find--you neither told them about it nor sent a copy of it to them nor bragged about it nor shared it with anyone you both know

It is exactly what it says, the harassment has to be intended and directed at a specific person.

If you hung a dummy by a noose. If you did it at school it may be at a group of people, or just at the school, not a specific person.

If you did it at school, but attached to a specific locker to had a name on it, or if you did it in front of someone's house.

I will assume this refers to your posting, the issue will be that on criminal charges they will need to show, it would be obvious to the average person that knows this person, that this is them. So if it is obvious you mean them, and you are posting things that are wrong, or untrue, or opinions that are not facts,

It will be up to the judge to decide if they meet this requirement.

Civil court will be a different issue, since the level of proof is less, but in civil court they have to prove a loss that can be measured by money