How to explain what "weird" is to a 4 year old?

Oh, but the kid’s got a point.

Instead of saying “that would be weird”, you could express the same sentiment better by saying “I wouldn’t want that” or “that would make me feel uncomfortable.”
You could also take this opportunity to teach them about personal boundaries.

‘Weird’ (in this context) is a word used to express a feeling of personal discomfort with established patterns being broken, but its usage implies that that feeling is a fact about the thing that causes it and not about you who feels it. It also implies that if something ‘is weird’, that thing is bad.
This kid’s mom is right to have a problem with that.

Weird is unusual, in this case also undesirable.

Weird has more than one meaning apparently. The motto for Austin, Texas is “Keep Austin Weird”. But I’m still not sure what that means.

Weird is a compliment in my house. I have always taught my kids that weird is the opposite of pedestrian, and there is nothing wrong with it.
Now, in your specific case, I agree with @Fyrius. You were really saying that you wouldn’t want him to pick your scab, and that it would make you feel uncomfortable. I can’t see how the term “weird” would apply to your situation.

Generally, I tell my children that ‘weird’ like ‘normal’ has no actual meaning. It’s a relative term, indicating whatever the person using it wouldn’t do or doesn’t feel comfortable with doing. So I tell my oldest, ‘you want to eat your boogers, fine by me, improves your immune system… do it in private, if you care how others look at you because they might think it’s weird but have no reason for it, really.’ So far, he’s given zero fucks.

We are all weird in our own ways.

I do agree with @Fyrius in one important way: It would be less pejorative to the child if you tell her “That would make me feel weird.”

I agree with the kid here. Weird in the way you used it does kinda have a negative connotation. Like others said above I would explain that it would make you feel uncomfortable.

I gotta be me

“Weird” is one of those umbrella words that is so overused as to have lost its meaning. Think of more specific synonyms or a short phrase to start a little dialog.

One explanation is that picking a scab on anyone’s body will possibly cause a scar. You can also acknowledge that we are all tempted to pick. If he asks “Why,” you say that you don’t know and ask her what she thinks.”

Why do you want to do that, sweetie?”

You are also teaching her something about language and communication.

Ugh, mom is pc.

“Weird, you know, like a octopus with only TWO arms.”

To explain what weird usually means, and put it in terms a 4-year old will grasp, paint a word picture of things they would find weird. “You get up one morning and walk outside, and everything you touch or step on just floats slowly up into the sky and disappears. That would be weird.” Of course, that would just raise the question in this bright kid’s mind, “Then what’s so weird about me picking your scab?”

Picking a scab isn’t weird, it is counterproductive. It causes further physical damage to an already damaged spot on your skin, and makes things worse. Now, DO NOT ask me how to explain that to a 4-year-old. :-)

Suppose you go to the toilet to pee. And when you do so the pee doesn’t go down into the toilet bowl, but straight up all the way to the ceiling. That’s weird.

A small child will realize that this is not possible.

@mattbrowne Yeah, and then they’ll try it. Stand by with the cleaning supplies!

Just tell wifey it sounded like a good idea at the time. ;D