Ok, I have searched google far and wide and the only answers I have found are:
a) A kinkless valve is a beam tetrode.
b ) A beam tetrode is kinkless
c) KT means Kinkless tetrode.
d) kinkless means it is kinkless.
And none of those answer the question.
My only idea is that a valve that is kinkless doesnt have a "kink" in its grid vs anode graph.
But I havent seen any valves so far that do have a kink!
This is driving me nuts...
Mark