Astatic \A*stat"ic\, a. [Pref. a- not + static.]

(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.

Source: Webster's Revised Unabridged Dictionary (1913)