Dictionaries are often described as defining words.
However, this doesn't hold up to examination.
Start at any point in a dictionary and you have a group of words 'defining' another word.
Look up each of that group of words and you find more words 'defining' each of that group. And so on until we either run out of words or we are using words that are indirectly 'defined' by themselves.
Every 'definition' in every dictionary is a tautology.
But language, and, indeed, dictionaries do work and are useful. So there is some fault in our assumption of how dictionaries work.
How dictionaries really work
Each 'definition' in a dictionary is, in fact, a label for a particular pattern of relationships. The group of words 'defining' each definition are actually describing a pattern of relationships - built on the pattern