The crossword solution for the term PSIS' PRECEDERS is CHIS, which stands for the Cervical Human Intervertebral Slices. This term refers to a type of anatomical structure found in the human spine, which consists of two adjacent vertebrae and the intervertebral disc between them. The CHIS are the precursors to the PSIS, or Posterior Superior Iliac Spines, which are bony protrusions located on the posterior superior iliac crest of the pelvis.