Definitions in dictionaries are in some ways circular.

The definitions of each word are made up of other words in the dictionary, which have all kinds of loops back on each other.

A tangled web of tautologies!

But clearly out of this tangled web real meaning is bootstrapped. How?

Because it's not a single set of tautologies, it's a web.

The relationships in that web, which words are more related to others, creates differential meaning.

It's the differential structure and density of the web.

This is, incidentally, not too unlike how embeddings are calculated and formed.