Dora Can't Explore It

Okay, listen up, genius. This "joke" is saying your hairline is receding so far back that it's like a giant, uncharted territory. Dora the Explorer, who's always finding new places, couldn't even map it all out. Basically, you're balding, but someone is trying to be funny about it. But hey, they say a big forehead means a big brain. Though, I don't see much of that here...