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

Four year old = F
Me = M
So the conversation went a little something like this:
Me scratching a bug bite
F: Your scratching your arm.
M: Yes, I have a bug bite.
F: Oooh so it itches?
M: Mhm.
F: But if you keep scratching it then it will make a scab.
M: I know. It’s a bad habit.
F: Ohh. Well when your scab comes can I pick it for you?
M: No. That would be very weird.
F: Weird? What is weird? My mom said that saying weird isnt good because it makes people feel bad.

How do I explain the concept of “weird” to this child?