astatic
/eɪˈstætɪk/adjective
1- not keeping a steady position or direction, in particular位置（或方向）不稳定的, 尤指：
1.1
- Physics (of a system or instrument) consisting of or employing a combination of magnets suspended in a uniform magnetic field on a single wire or thread in such a way that no torque is present (e.g. to minimize the effect of the earth's magnetic field)【物理】（系统, 仪器）无定向的, 无静差的。
词源
early 19th cent.: from Greek astatos 'unstable' + -IC.