Mainly English Language, Some Multilingual
Eric Weisstein's World of Astronomy Encyclopedia
A Wikipedia-type, English-language illustrated glossary and encyclopedia of astronomy.
Agriculture / Botany / Horticulture
Agriculture Glossary - House Committee on Agriculture
A glossary of agricultural terms, programs and laws from the Congressional Research Service, Library of Congress.
FAO TERM PORTAL
Thematic glossaries from the Food and Agriculture Organization of the United Nations in Arabic, Chinese, English, French, Russian and Spanish. Subjects include Aquaculture, Climate Change, Organic Agriculture, etc.
GardenWeb Glossary of Botanical Terms
Currently contains 4400 terms relating to botany, horticulture and landscape architecture and is regularly updated (English only).
The Virtual Library of Botany/Plant Biology
Hundreds of links related to plants, agriculture and biosciences maintained by the University of Oklahoma.
Glossary of Biochemistry and Molecular Biology
Up-to-date English-language glossary containing 3,000 terms from Portland Press Ltd.
The Bartleby.com edition of Gray's Anatomy of the Human Body features 1,247 engravings--many in color--from the classic 1918 publication as well as a subject index with 13,000 entries ranging from Antrum of Highmore to the Zonule of Zinn.
A free chemistry search engine that aggregates other sites, such as NCBI and PubChem. If you search for a chemical, it will return information including properties, sources, and links to journal articles, web articles, and MSDS's. Nice advanced search options, including structural.
Eric Weisstein's World of Chemistry Encyclopedia
A Wikipedia-type, English-language glossary and encyclopedia from Wolfram Research.
Material Safety Data Sheets
Material Safety Data Sheets for chemical products from 50 countries in multiple languages, including traditional and simplified Chinese, French, German, Korean, Japanese, Russian and Spanish. Contains country specific regulatory information.
Climate & Environment
Climate Change Glossaries
Links to glossaries of terms used in the Assessment Report of the Intergovernmental Panel on Climate Change (IPCC), a scientific intergovernmental body set up by the World Meteorological Organization and the United Nations Environment Program. Glossaries are available in Arabic, Chinese, English, French, Spanish and Russian.
European Environment Agency Glossary
Multilingual glossary with 10,000 terms. “In this terminology site you find the most complete list of all the environmental terms used in several websites created or contributed by the European Environment Agency (EEA).” Definitions in English. The EEA website also contains many full-text documents and reports in other languages.
Global Change Master Directory Links Page
From NASA. Links to websites relating to all areas of earth science, including climate, environment, GIS, geology, geography, etc. Has a link to the Global Change Master Directory List of Earth Science Acronyms, Glossaries and Gazetteers. Some bilingual glossaries available but most are in English.
GEMET (GEneral Multilingual Environmental Thesaurus)
Multilingual (27 language) thesaurus from the European Environment Information and Observation Network – the reference vocabulary of the European Environment Agency (EEA) and its Network (EIONET).
National Weather Service Glossary
Contains information on more than 2000 terms, phrases and abbreviations used by the NWS. Extremely detailed and technical.
Avibase – the world bird database
Avibase is an extensive database information system about all birds of the world, containing over 3.5 million records, about 10,000 species and 22,000 subspecies of birds, including distribution information, taxonomy, synonyms in several languages and more. Hosted by Bird Studies Canada, the Canadian copartner of Birdlife International.
Fish Names in the European Community
Multilingual list of fish names from the FAO (Food and Agriculture Organization of the UN). English and scientific names, followed by the chosen common names in as many other languages as possible, including Danish, Dutch, French, German, Greek, Italian, Norwegian, Portuguese and Spanish.
An open, free directory of species, covering animalia, plantae, fungi, bacteria, archaea, protista and all other forms of life. Contains almost 200,000 taxanomic entries, in all T&I languages.