Geology Dictionary - Geology.com
- Definitions of terms, written at a level appropriate for students in introductory courses.
- http://geology.com/geology-dictionary.shtml

Schlumberger Oilfield Glossary
- Defines many terms related to oil and gas exploration and production. Includes illustrations.
- http://www.glossary.oilfield.slb.com/

Geological and Gem Terminology
- Jillian Banfield's glossary of geological and gem-related vocabulary.
- http://seismo.berkeley.edu/~jill/glossary.html

Volcanic and Geologic Terms Glossary
- Common terms defined.
- http://volcano.und.nodak.edu/vwdocs/msh/llc/is/vgt.html

USGS Photo Glossary of Volcanic Terms
- Illustrates and describes commonly used volcano-related terms.
- http://volcanoes.usgs.gov/Products/Pglossary/pglossary.html

Earthquake Image Glossary
- Heavily illustrated glossary of common terms in seismology.
- http://earthquake.usgs.gov/image_glossary/

Glossary of Selected Geologic Terms
- Glossary of selected geological terms from the University of Nebraska-Lincoln.
- http://csd.unl.edu/general/glossary.asp

Glacier Glossary
- An A-to-Z glossary of glacier terms written by the professor and students of an NEIU glaciology class.
- http://ebeltz.net/glacier/glacglos.html

GeologyLink Glossary
- Indexed glossary of geology terms.
- http://college.hmco.com/geology/resources/geologylink/glossary.html

Dictionary of Petroleum and Oilfield Terminology
- Glossary of terms. The list is searchable and also contains links to further information.
- http://www.anson.co.uk/oilfield_glossary.html