The breaking was a term used by the Yuuzhan Vong to describe a torture technique they employed against captives.
This form of torture involved the use of mental torment instead of physical one in order to subdue the prisoner before obtaining useful information from them. The captive's senses and determination were slowly broken by constant verbal degradation until the victim was mentally broken to the point that they were incapable of functioning anymore. These broken individuals tended to sob like children and were not able to think rationally.
It was common for the Yuuzhan Vong to bombard their prisoner with images of the expected horrors they were to face and their terrible deaths.
Jedi Knight Miko Reglia was broken by a yammosk near the start of the Yuuzhan Vong. Wurth Skidder was subjected to the telepathic predations of the yammosk of the Clustership Crèche as part of his breaking once his identity as a Jedi was discovered.
Duman Yaght used voxyn on his ship, the Exquisite Death, as a method of torturing the Myrkr strike team when they allowed themselves to be captured in order to infiltrate the worldship around Myrkr.