San An·dre·as Fault (s?n ?n-dr???s) A major zone of fractures in the earth’s crust extending along the coastline of California from the northwest part of the state to the Gulf of California. Movement of the tectonic plates along the fault has caused numerous tremors, including the devastating San Francisco earthquake of 1906.American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.San? An?dre?as fault? (?sæn æn?dre? ?s) n. an active geological fault in the western U.S., extending from San Francisco to S California. [after San Andreas Lake, located in the rift, in San Mateo County] Random House Kernerman Webster’s College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.