I hear about it frequently, especially on certain talk shows on the radio. But I'm not sure what it really means if we default on our debt.
How does that work if we actually default on our debt as a nation?
If we default, we are simply deciding not to pay back what is owed. It's unlikely to happen, as your credit rating will be at junk status and no one will likely lend you money again for a very long time.
This is an entirely different situation than inflation away the debt by essentially "printing money" (inflating the money supply).
I'm not sure about the legality of defaulting, but it's obviously entirely possible. The government could simply refuse to pay the bills as they come due. Allegedly, according to legal theorists, the federal government cannot declare bankruptcy (which is different than defaulting) as it is sovereign. An additional fun fact is that, according to the US government, they are immune from all lawsuits unless they voluntarily surrender said sovereign immunity. So technically they could just stop paying certain bills and then claim that they can't be sued for recovering assets.