Словарь WordWeb

WordWeb is a free English thesaurus and dictionary for Windows, and can be used to look up words from within almost any program in just one click. It works off-line, but can also look up words in web references such as the Wikipedia encyclopedia. Features of the free version include:

Definitions and synonyms
Proper nouns
Related words
150 000 root words
120 000 synonym sets
Look up words in almost any program

Особенность - словарь с закладками.
Существует бесплатная тестовая версия. Полная версия словаря стоит от $29.
Сайт программы WordWeb