Top Definition
A woman who's emotions turn from happy (or at least normal) to raging cunt in the blink of an eye for no apparent or good reason.
I was minding my own business when she turned instacunt on me.

We were getting along just fine, when all of a sudden she went instacunt on me and told me to get the fuck out.
by BizzyBlond October 08, 2009
9 Words related to Instacunt

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