"Monster" is not a catch-all term for evil creatures. Ted Bundy was evil, scary, and had strange teeth, but that is not enough to make him a "monster." To be a true monster, you need to have some super-natural skill at being evil and scary. It also helps to be blue, but that's really a secondary qualification.
I am adamant in this, because there really are monsters in this world. Monsters that become very, very angry when humans mistakenly identify non-monsters as monsters. It's a touchy subject for them, and who can blame them? Imagine if your boss were to consistently mistake you for a fern. You'd be offended too.
It always helps to have a list of concretes to solidify your understanding of a definition, so I've compiled a list of some real-life monsters for you to peruse.
Geese are clearly monsters. They have a truly unmatched capacity for evil. They are especially dangerous to children, who tend to learn about ducks first. A child learns "Duck + Bread = New Best Friend" very quickly.
When a child sees a goose for the first time, they see a really big duck and they think "Big Duck + Lots of Bread = Super Best Friend."
The goose sees something more like this:
What follows can only be explained in slow motion:
I have witnessed a squirrel stealing a double cheese burger *out of a person's hand* through a combination of acrobatic skill, Special Forces stealth, and sheer ballsiness. I have seen a squirrel steal an entire pack of cigarettes from a purse, climb up a tree with them, and start eating them. And in Russia, *squirrels ate a dog* in less than a minute. I think this proves squirrels belong solidly in the monster category.
3. Bat-Eating Centipedes
I think it bears repeating that this is the scariest thing in the known universe. Its existence requires an immediate and radical alteration to our survival strategy as a species.
I hope we are all better informed, now. Remember: there are monsters out there. Respect them, or they will kill you.