There are many online glossaries of GIS terms and acronyms. We recommend you compare the definitions from three sources to get a comprehensive idea of what the term means.
GIS Wiki: wiki.gis.com
Dictionary of Abbreviations and Acronyms in GIS, Cartography, and Remote Sensing—University of California at Berkeley
FGDC Glossary—most terms are from the Spatial Data Transfer Standard (FIPS 173)
Geographer's Craft Glossary—University of Colorado at Boulder
Glossaire SIG—French-language glossary from ESRI-France
Glossary of Cartographic Terms—Perry-Castañeda Library, University of Texas at Austin