1 definition by drewdaspot

A girl who you will become your wife if the two of you are single at a pre-determined age.
Robin: Let's make a pact, if we both turn 40 and we're both single..
Ted: Robin Scherbatsky, will you be my Back-Up Wife?
Robin: A girl always dreams of hearing those words. Yes, yes, a million times, yes!
by drewdaspot March 4, 2012
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