Webster's English Dictionary

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gyroscope

gy.ro.scope \'ji--r*-.sko-p\ \.ji--r*-'ska:p-ik\ \-i-k(*-)le-\ n [F, fr. 
   gyr- + -scope; fr. its original use to illustrate the rotat]ion of the 
   earth : a wheel or disk mounted to spin rapidly about an axis and also free 
   to r otate about one or both of two axes perpendicular to each other and to 
   the axis of spin so that a rotation of one of the two mutually 
   perpendicular axes results from application of torque to the other when the 
   wheel is spinning and so that the entire apparatus offers considerable 
   opposition depending on the angular momentum to any torque that would 
   change the direction of the axis of spin - gy.ro.scop.ic aj