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

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

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

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

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

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

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

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

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

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