Teaching the meaning of a word is like...

...trying to describe a dog.

Imagine that I show up on your doorstep one day. You open the door, and I say:

Hi, I'm looking for my dog who's gone missing. She's about a foot tall, with short legs and a long, round torso. Her face is kind of scrunched up and she has big eyes. Her hair is short and a little shaggy.

If you've seen me walking my dog around the neighborhood, you'll understand my explanation perfectly. You'll nod your head and say, "Oh yeah, I know the dog you're talking about. She was running around in my yard earlier today." 

But if you've never seen my dog before, you won't really know what it looks like just based on my description. I'll probably forget to tell you about the length of its tail, the color of the hair on its ears, the way that it walks, and other things. If I did a good job of describing her and you see her walking down the street a few minutes later, you may say, "Hey, that must be the dog that the guy next door was asking about!" But you probably won't remember my description a week later.

Trying to explain an English word or phrase is a lot like describing that dog. I can give you a little bit of information about what it means, but I can't explain everything. If you've heard or read it before, you might know what I'm talking about, but if not you'll soon forget most of my explanation.

My only hope is that, after you read my explanation, you'll come across that word or phrase somewhere in the next few days, and your eyes will light up as you say:

"Hey! That must be the phrase that the guy on PhraseMix was talking about!"