Is there anything that defines words other than the dictionary?

We the users define the words.  The dictionary simply reports the most typical meanings (what we all accept as a general thing).  I do not know of any other source books whose purpose is the compilation of word meanings.

There are two other books that deal with word usage and history. If you're looking for formal written works

Encyclopedias. These set of reference works that delve deeper into words and other subject than any other reference works. Going into the long history and evolution of words.

Thesaurus. A reference work that gives synonyms and antonyms and offers definitions somtimes.

A dictionary simply records usage at the time it is compiled.

General usage tends to define words more, since not all words or senses in which said words are used are in þe dictionary