The half sister of your half brother or half sister.
I got to see my unsister on Thanksgiving.
by ridl February 26, 2009
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It’s an action you do when you ‘sister’ forgets about you and forgets about you in posts or tags and is being a dick. So you have to unsister her as a sister.
Friend1: I think I’m going to unsister her
Friend2: OMG NO WAY YOUR unsistering HER!
by max luckwood August 23, 2018
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an action used when you unsister someone because your ‘sister’ forgets about you daily and stops posting about you not texting you.
Friend 1: Im going to unsister her

Friend 2: Omg no way you are insistering her

So you see unsistering is a word/ action used when a friend wants to be a dick and forget you
by max luckwood August 23, 2018
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