It may be worth mentioning for the benefit of non-aviators and new ones that the "yo-yo" expedient described by Centaurus would most probably be used after a runaway HS, in order to unload the HS sufficiently to restore its ability to be moved. If the runaway took place following a nose-down trim adjustment - as typically required during flap retraction and/or a go-around in a contemporary jet airliner with engines mounted under the wings - the first priority for the pilot(s) may be to select enough up-elevator to stop the aircraft nose diving into terrain.
Yes, safetypee, the failure of a serviceable trimming system to move an aerodynamically-overloaded HS is generally referred to as a "stall" of the HS jack.