The loosest definition might be "isolated network or leaf node of the internet" if one considers a non-natted DMZ to be a lan. If one thinks all the assumption

The loosest definition might be "isolated network or leaf node of the internet" if one considers a non-natted DMZ to be a lan. If one thinks all the assumptions in the article are bogus, then I agree there's no definition of the term. >99% of the time, being natted and/or having private address space is the definition.