Call me the walking dictionary

My 4-year-old-son, lovingly referred to as the Superhero, keeps asking what various words mean. It's mostly fun, until I have no idea how to define the word in question without using said word.

For example, on our way to my weekly women's group today he asked, "Mommy, when will we get there?"

"In just a few minutes."

"What does 'a few minutes' mean?"

"It means really soon"

"What does soon mean?"

"It means quickly."

"What does quickly mean?"

"It means fast."

"What does fast mean?"

"Um, not slow." I'm running out of words and answers at this point.

"What does slow mean?"

And at that one, I reply, "Buddy, I'm not sure how to answer that one. What do you think it means?"

"I don't know. When will we be there mommy?"

And the game continues until we arrive 10 minutes later. I think I may need to begin carrying a Thesaurus from now on.