gy-ro-scope:
	A wheel or disk mounted to spin rapidly about an axis and also
	free to rotate about one or both of two axes perpindicular to
	each other and 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.
		-- Webster's Seventh New Collegiate Dictionary