Expanding Vocabulary

Cat and I learned a new word today from Nathan: ropaster. We have no idea what it means, but he made certain that we learned it. We were leaving the parking lot at lunch and he pointed over to the construction site in downtown Rockville where they're expanding the county courthouse building. It's a multistory structure and they have a huge crane erected for the project. We're fairly certain that Nathan was pointing to the crane when he used this mysterious word. I got in the car after the conversation had already started, but it went something like this:

Nathan: Mommy, look at the ropaster over there!

Cat: What?

Nathan: The ropaster!

Cat: The what?

Nathan: The ROPASTER!!!

Cat:  What is a ropaster?  Are you talking about the crane over there?  Or the steeple?  Or the flagpole?

Nathan: NO!!!  The ROPASTER!!!

Me: Nathan, what are you talking about?  What is a ropaster?

Nathan: THE ROPASTER!!!  You guys gotta stop being funny!

Me: I see that big crane over there.

Nathan: NO!!! I'M TALKING ABOUT THE ROPASTER!  YOU GOT TO LISTEN TO ME, GUYS!

Both of us: Oh, the ropaster.  Yes, we see it.  It's a big one!

I don't know if we'll ever figure that one out.