what's a 'pelvic gimbal"?

WTF is it that titanium starscream makes ornaments out of?
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• Gimbal
A gimbal is a mechanical device that allows the rotation of an object in multiple dimensions. It is typically made up of two or three pairs of pivots, mounted on axes at right angles. A three-axis gimbal may allow an object mounted on it to remain in a horizontal plane regardless of the motion of its support. Shipboard compasses, chronometers, stove and even drink holders are typically mounted on gimbals to keep them level to the horizon at all times.