It's all about the time scale. Cox, for instance, on my $50/mo plan, offers peak bandwidth of 20Mbit/sec (so that picking up an MP3 from Amazon is nearly instantaneous), sustained average bandwidth of 5Mbit/sec (time scale unspecified, but my observations suggest it is 1 minute), and monthly average bandwidth of 40GB/month. They threaten to terminate you if you go over the monthly cap - which is dumb. They should do something like TW and either charge you or lower your peak.
So perhaps the term you are looking for is "average bandwidth" for some time period the average is taken over.
While the pricing seems a little high, I am *glad* that Time Warner is coming clean about the limitations of their service. A little competition will fix the pricing real quick.
Rather than automatically charge you more, some ISPs simply lower your peak bandwidth to ISDN levels - so that you still have (slow) internet access, and then offer to upgrade your monthly average for more dough. The peak bandwidth is restored as soon as the monthly average goes below the cap again.
I also think the "unlimited" advertising is a truth in advertising issue - and any company that advertises "unlimited" and then starts throttling you when you use "too much" should be prosecuted by the government for false advertising.