flash memory n. A form of nonvolatile RAM that is typically smaller, lighter, and more energy efficient than a hard drive, used especially in handheld and portable devices. 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.flash? mem?ory n. Computers. a type of reprogrammable memory that retains information even with the power turned off. [1990?95] Random House Kernerman Webster’s College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.