Are there no limits to unlimited data plans? Yes there are limits to unlimited plans. The new "Unlimited Above"plan offered by Verizon has limits that are above the limits of it's other unlimited plans. Edit: should be "Above Unlimited" plan, to be precise.
That new Verizon plan then most likely falls in the category of limited unlimited plans. That new plan is likely not in the category of unlimited limited plans, such as the throttled LTE (or straight 2G) of some plans.
Perhaps it has been done already, but, if not, we should soon see some new entries in the O.E.D, and other dictionaries, listing new definitions and usages of the word "unlimited" since it has been used by the ISPs and telecom providers in unique and accepted(?) ways for some time now.