Architecture

The Conservation Glossary - Architectural, building and conservation terms explained by Neil Grieve of The Centre for Conservation and Urban Studies, University of Dundee.
http://www.trp.dundee.ac.uk/research/glossary/glossary.html

Castle Glossary - A full glossary from Castles of Britain.
http://www.castles-of-britain.com/castle38.htm

Gardens Guide - Glossary of terms used by garden historians and landscape architects, with links to examples in eTexts.
http://www.gardenvisit.com/glossary/glossary.htm

Architectionary.com - A searchable architecture and construction related dictionary. All entries can be freely edited by the public.
http://www.architectionary.com

Probert Encyclopaedia: Architecture - An illustrated a-z of architectural styles and terminology.
http://www.probertencyclopaedia.com/architecture.htm

California Missions Studies Terms - Illustrated glossary of terms relating to California missions and other Hispanic sites by Sasha Honig.
http://www.ca-missions.org/illusgl.html

Glossary of Medieval Art and Architecture - An illustrated and cross-referenced dictionary of mainly architectural terms from Jane Vadnal of the University of Pittsburgh.
http://www.pitt.edu/~medart/menuglossary/

Art and Architecture Thesaurus - A structured vocabulary from the Getty Trust of more than 125,000 terms for describing fine art, architecture, decorative arts, archival materials, and material culture.
http://www.getty.edu/research/conducting_research/vocabularies/aat/

Art and Architecture - Single-page glossary of art and architectural terms, from Your Way to Florence.
http://www.arca.net/tourism/glossary.htm

Architectural Terms - An illustrated glossary by Alice Cotton.
http://www.artemisillustration.com/assets/text/Ornamental%20%20Terms_Glossary.htm

Buffalo Illustrated Architecture Dictionary - Indexed, cross-referenced and illustrated dictionary of architectural terms from Chuck LaChiusa. All examples are from buildings in Buffalo, New York.
http://ah.bfn.org/a/DCTNRY/vocab.html

A Dictionary of Military Architecture - A dictionary of military architecture, fortification and fieldworks from the Iron Age to the eighteenth century by Stephen Francis Wyley.
http://www.angelfire.com/wy/svenskildbiter/madict.html