A corker of a question ! Then to begin an answer ...
Knowledge without words (1) - the math. example
Nineteenth-century German mathematician Carl Friedrich Gauss used
to joke that he could calculate before
he could talk. Maybe it was no joke. Recent
work casts doubt on the notion that language underlies mathematical ability and
perhaps other ...
... and the dictionary being just a set of self-references would be completely useless.
You've just noticed that knowledge (not only regarding the term) is based on a set of tautologies. Kant already suggested that. In such case we can take it to the extreme: you are asking a useless question, since any answer would be based on facts you already know.