the anniversary of the day you broke up with your spouse/significant other.
the great thing about a noniversary is you don't have to spend any cash, unlike an anniversary
What might have been an anniversary had the relationship worked out, but it didn't and you either want to seem cool about it or bitchy. Either way works depending how you use it.
(after breaking up)
Kate: you know what today is right?
Kate: the day we started dating silly!
Nick: right, which we aren't anymore...
Nick: happy noniversary?
Kate: awhhh <3 i regifted the bear you got me by the way.
how non-couples (aka friends with benefits) celebrate the passage of time
Me: For our one-year noniversary, Ben took me back to Charlie's where we had our first date.
Friend: Aww...how sweet.
Me: I know, right. But he still isn't willing to update his FaceBook status.
An anniversary of something that is no longer in existence, or not very significant anymore.
"Today is the 1 year noniversary of me and Edward's first kiss"