As mentioned above, inverted index extraction (IIE) is one of the earliest attempts at using dictionary definitions to extract synonyms or related words.
for a given target word t , the entire dictionary is scanned in search of words whose definition texts contain t, and such words are considered related to t. Since both synonymy and relatedness are symmetric, it is equivalent to say that every definiendum is related to all its definientia, or that the dictionary graph is an unweighted, undirected graph where every pair of neighbors is considered equally related.