not having the same center, as two circles one inside the other
not having the axis exactly in the center; off-center: an eccentric wheel
not exactly circular in shape or motion
deviating from the norm, as in conduct; odd; unconventional
noun
a disk set off center on a shaft and revolving inside a strap that is attached to one end of a rod, thereby converting the circular motion of the shaft into back-and-forth motion of the rod