Unfortunately the terminological mismatch arises because different physicists use the terms differently in different contexts.  For example, here is how Landau and Lifshitz define an adiabatic process:

> Let us suppose that a body is thermally isolated, and is subject to external conditions which vary sufficiently slowly. Such a process is said to be *adiabatic*

As you can see, these authors combine the criterion of thermal isolation (no heat exchange with the environment) with a slowness assumption, to arrive at their definition of the term adiabatic.  In contrast, consider Huang's definition of adiabatic in the context of thermodynamics;

>Any transformation the system can undergo in thermal isolation is said to take place adiabatically.

I would say, from personal experience, that the more modern convention for the term adiabatic is not the one used by Landau and Lifshitz.  In particular, most physicists I know use the term adiabatic in the context of thermodynamics to mean thermally isolated, while they use the term adiabatic in the context of quantum mechanics to mean sufficiently slow that certain approximations can be made.

**Addendum.** In the context of thermodynamics, the free expansion of a thermally isolated ideal gas is often referred to as an "adiabatic free expansion of a gas," see, for example [here][1].  Such a process is not isentropic.  Using Slavik's definition would deem invalid the characterization of such a free expansion as adiabatic.  However, all you need to do is google "adiabatic free expansion" to see how widespread such use of the terminology is.

People can make all of the unqualified, seemingly confident statements about what the term "adiabatic" means, but it's simply false that everyone uses the same definition, and I think its unproductive to call widely used conventions other than your own "not sensible."


  [1]: http://en.wikipedia.org/wiki/Adiabatic_process#Adiabatic_free_expansion_of_a_gas