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

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

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

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