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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The next person in line that you ask to do something with after your preferred person isn't able to.
guy 1: "My girlfriend can't make it for lunch with me today...do you want to go?"
guy 2: "What, am I your back-up bitch?"
by RNPS August 29, 2007
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Coming home from any vacation and keep on getting circular or very round bullets of shit until you have this massive motherload of a fuck come out and you have the squirts for the rest of the time. Most common in Disney Locations due to the massive sorts of food and re-used crap in the food and water.
Mom: Hows my baby timmy...
Coroner: He died from Disney Back-Up
Mom: ....
by MaZe000 March 29, 2008
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an acquaintance that is only spoken to when all of one's real friends are absent.
A: Why were you talking to Erik that other day?
B: Dude, he's just a back-up friend. nobody else was around worth talking to.
by assgoblin82 January 31, 2007
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A friend who isn't really part of the group, but who you hang out with when the rest of the group is gone.
Why isn't Kailyn paying any attention to Meggie?

Oh, Meggie's just her back-up friend. She's talking to Ashley right now.
by Sleet October 23, 2009
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Person you invite to go somewhere when your preferred person cannot go. Can be male or female (non-gender specific).
"You can't make it? I better call my back-up bitch!"
by Rob Norment March 30, 2007
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There are usually "back-up channels" in which to people use in times when all other channels are on adverts. This saves people from being bored and changing activity to going outside or reading.
Dude - "I'm so glad we have this back-up channel.. i mean police camera action is pretty boring but i'm glad we're not watching some shitty adverts.
Dude-et - "yeah the adverts these days are just all for freakin injury lawyers.."
by Jonny Clarke July 5, 2009
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