twin bedn. A bed intended to fit one individual, usually measuring about 39 by 75 inches (99 by 190 centimeters), and traditionally one of a set of two.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.twin bed n (Furniture) one of a pair of matching single beds Collins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014twin? bed? n. a twin-size bed, esp. one of a matching pair in a bedroom; single bed. [1915?20, Amer.] Random House Kernerman Webster’s College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.