typographical errorn. A mistake in printing, typesetting, or typing, especially one caused by striking an incorrect key on a keyboard.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.typograph?ical er?ror n. an error in printed or typewritten matter resulting from a mistake in typing or from mechanical failure. Random House Kernerman Webster’s College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.