oakmoss (???k?m?s) n (Plants) a type of lichen, or the essence produced from it, that is commonly found growing on oak trees and from which can be produced an essence that is used in the manufacture of perfumesCollins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014oak?moss (?o?k?m?s, -?m?s) n. a lichen, Evernia pranastri, growing on oak and other trees, yielding a resin used in the manufacture of perfumes. [1920?25] Random House Kernerman Webster’s College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.