A Writer's Guide to Sassy Synonyms - Promotion for a reference guide to assist in finding the right word to use in place of "said", "replied", "asked" etc.
ARTFL Project: ROGET'S Thesaurus Search Form - Uses the Gutenberg Project text.
Astronomy Thesaurus - astronomy terms in English, French, German, Spanish and Italian; all terms cross referenced.
CAS General Subject Vocabulary Helper - Extensive listings for chemistry. Produced by Chemical Abstracts Service, a division of the American Chemical Society.
Eurodic Autom - European Union terminology. Available on most European Union languages.
Freeality Internet Search Thesaurus - Search for words, phrases, and quotations. Links to language tools, reference and research and reverse lookup.
Getty Art and Architecture Thesaurus - searchable database of vocabulary and terms for describing objects, textural materials, images, architecture and material culture from antiquity to the present.
Getty Thesaurus of Geographic Names - search on place and feature names worldwide. Results identify location contextually, ie what state or province a city is in, and by coordinates.
Global Legal Information Network (GLIN) Thesaurus
HIV/AIDS Treatment Thesaurus - standardized bilingual (French and English) tool, created to organize and find information in the field of HIV/AIDS treatment information. Non-preferred terminology covers variant spellings.
Intelligent Transportation Systems (ITS) Thesaurus - Microthesaurus based on the Transportation Research Thesaurus.
Legislative Indexing Vocabulary - developed for use with legislative and public policy subject matter.
Lexical Freenet - Allows you to search for relationships between words and concepts that might never have occurred to you before.
Library of Congress Thesauri
Merriam-Webster Thesaurus
NASA Thesaurus - National Aeronautics and Space Administration Thesaurus. Extensive coverage of scientific terms.
OECD Macrothesaurus - Organization for Economic Co-operation and Development. Available in English, German, French, and Spanish. Thesaurus of sociological and economic issues pertaining to international development.
Phrase Finder - Enter a single word and it will return a list of phrases and sayings that are related to the word in some way. In English.
Plumb Design Visual Thesaurus - an exploration of sense relationships within the English language. By clicking on words, you follow a thread of meaning, creating a spatial map of linguistic associations.
Railroad Definitions - The most complete online railroad glossary: more than 400 entries. Contains American, British, South-African railroad-related terms and slang.
Roget's Thesaurus - Roget's Thesaurus of English words and phrases.
Roget's Thesaurus - As distributed by Project Gutenberg - Etext of Roget's Thesaurus No. Two, which is derived from the version of Roget's Thesaurus published in 1911.
Roget's Thesaurus [nih.gov]
Roget's Thesaurus Search Form
Sybrina's Phrase Thesaurus
Synonyms Dictionary
The Astronomy Thesaurus - Astronomical terms. Searches may be performed in English, French, German, Italian, and Spanish.
Thesaurus for Graphic Materials I: Subject Terms (TGM I) - consisting of 5,997 terms and numerous cross references indexing visual materials.
Thesaurus for Graphic Materials II (TGM II) - more than 600 terms, developed by the Library of Congress Prints and Photographs Division, with input from other archival image repositories.
Thesaurus Gopher
WordNet - a Lexical Database for English - An on-line lexical reference system whose design is inspired by current psycholinguistic theories of human lexical MMMMMM. English nouns, verbs, adjectives and adverbs are organized into synonym sets, each representing one underlying lexical concept. Different relations link the synonym sets. From the Cognitive Science Laboratory, Princeton University
Wordsmyth Educational Dictionary-Thesaurus - Integrated english dictionary and thesaurus.
WWWebster Thesaurus - Merriam-Webster Thesaurus