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1. A liability

2. Somebody with no training, no experience and no common sense or judgement insists on tagging along they are a "Nathalie Portman".

Origin- In the film Leon Nathalie Portman plays a child who loses her parents and is taken in by the assassin, Leon. She then informs a hotel receptionist he is her "Lover", fires random shots off a balcony window and ends up getting Leon killed.
You just lost us the game, you're such a Nathalie Portman.
by ThEyeball Kid December 13, 2010