MathWords.com, Annenberg Learner and Ditutor provide lists of geometry terms and definitions from A to Z. MathWords.com offers terminology regarding plane and solid geometry as well as basic triangle trigonometry. This website is in alphabetical order but also has an index to search by letter or subject area.
Annenberg Learner, at Learner.org, provides an alphabetically sorted index of key geometry terms. This website is a teacher resource for professional curriculum development and also contains geometry sessions, videos and support materials.
Ditutor provides an index of geometry terms. This website sorts the set of geometry terms both by letter and by subject, including angles geometry, geometry math, triangle geometry and plane geometry.