astat·ic /əˈstætɪk/ 形容詞
  不穩定的,非靜止的,無定向的,無靜差的
  A·stat·ic a.  Magnetism Having little or no tendency to take a fixed or definite position or direction: thus, a suspended magnetic needle, when rendered astatic, loses its polarity, or tendency to point in a given direction.
  Astatic pair Magnetism, a pair of magnetic needles so mounted as to be nearly or quite astatic, as in some galvanometers.
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  astatic
       adj : not static or stable