- The definition of either or is an expression used to indicate that there are only two options or that both of two options are acceptable or equivalent.
An example of either or is when you are offered either spaghetti or cereal for dinner and are different between the two so you say "either or" to indicate that both would work.
either-or definition by Webster's New World
Webster's New World College Dictionary Copyright © 2010 by Wiley Publishing, Inc., Cleveland, Ohio. Used by arrangement with John Wiley & Sons, Inc.
designating a proposition, situation, etc. limited to only two alternatives
either-or definition by American Heritage Dictionary
A strictly limited choice or division between only two options.adjective
Of or characterized by a choice or division limited strictly between two options: found ourselves in an either-or situation.