I'm still here as well. Will probably get a post up within a few hours, I'm in that kind of mood. Still trying to decide what Lena is thinking about the easy-bake mirror-thingy.
I've personally never seen a dire wolf called a monster. Not saying it doesn't happen.
My first reaction to seeing a question like this is to simply look at a dictionary. According to dictionary.com...
1. a legendary animal combining features of animal and human form or having the forms of various animals in combination, as a centaur, griffin, or sphinx.
2. any creature so ugly or monstrous as to frighten people.
3. any animal or human grotesquely deviating from the normal shape, behavior, or character.
4. a person who excites horror by wickedness, cruelty, etc.
5. any animal or thing huge in size.
6. Biology.
an animal or plant of abnormal form or structure, as from marked malformation or the absence of certain parts or organs.
a grossly anomalous fetus or infant, especially one that is not viable.
7. anything unnatural or monstrous.
As you can see, most if not all of Antarctic Termite's points were true. The word has been around for a long time, and has gained a lot of different meanings. The one over branching detail is that monsters have the power to scare most humans.
Animals are the creatures that exist in the real world and monsters are the ones that doesn't. But how about the characters in the game/book/movie? Surely, to them the difference between a wolf and a dire wolf is just size, just like between a bear and a grizzly bear. So how does one define a monster in a world where both animals and monsters are natural?
Here's what I came up with after thinking on it for a while:
A monster is any non-sentient creature that goes out of its way to menace and attack other creatures in and outside of its ecosystem for reasons that are not natural. Signs that you may be dealing with a monster are:
1. An inordinate number of the creatures kills are not consumed or used in any way.
2. The creature is actively destructive to its ecosystem and/or environment.
3. The creature demonstrates a willingness to go above and beyond what would be expected of a predator in pursuit of food, such as a willingness to scale fortified walls to kill those living within or attacking armed sentients when it is clearly strong enough to hunt for easier prey.
4. Persistence to the point of recklessness.
5. A willingness to incur injury in order to attack others.
6. A willingness to fight on even having sustained wounds that would cause a normal animal to abandon its hunt.
7. Any behavior that can be construed as "cruel" or "malicious" on the part of the creature where a rational explanation for the behavior can not be found.