Las·sen Peak (l?s??n) A volcano, 3,187 m (10,457 ft) high, in the Cascade Range of northern California. It erupted intermittently from 1914 to 1921 after 200 years of dormancy.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.Lassen Peak (?læs?n) n (Placename) a volcano in S California, in the S Cascade Range. An area of 416 sq km (161 sq miles) was established as Lassen Volcanic National Park in 1916. Height: 3187 m (10 457 ft)Collins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014Las?sen Peak? (?læs ?n) n. an active volcano in N California, in the S Cascade Range. 10,465 ft. (3190 m). Random House Kernerman Webster’s College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.