Ambisinistrous, adjective: clumsy or unskilled with both hands. 

It's the opposite of ambidextrous. 

Both ambisinistrous and ambidextrous come from latin "sinistra" and "dextra", meaning "left hand" and "right hand" respectively.

So ambidextrous means that both hands are like right hands, and ambisinistrous means both hands are like left hands. This presumes that left hands are intrinsically clumsy and unskilled compared to right hands, which is a true presumption for about 85% to 92% of the global population.[1]

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