This thesaurus/dictionary can be used to look up words from almost any program.

In addition to displaying sense definitions and synonyms, WordWeb can find sets of related words.

The database has more than 150,000 root words and 120,000 synonym sets, many proper nouns, pronunciations, and usage tags. WordWeb works off line, but when online you can also quickly view Web references such as the wikipedia encyclopedia. Version 5.51 includes updated databases.

Get it here: WordWeb