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A strictly limited choice or division between only two options.
Of or characterized by a choice or division limited strictly between two options: found ourselves in an either-or situation.
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.
presenting an unavoidable need to choose between two alternatives: an either-or situation.
Collins English Dictionary – Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014
1. restricted in choice to two options: an either-or situation.n.
2. a choice having only two options.
Random House Kernerman Webster's College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.