This is the number of times an adjacency has been rejected on this circuit. It counts adjacency formation attempts that got far enough to be evaluated by IS-IS but were explicitly rejected, commonly due to authentication failure, area address mismatch, or an incompatible circuit configuration between the two sides, making it the counter to check once ciiCircInitFails rules out a lower-layer problem. For example, two neighboring routers configured with mismatched area addresses would see ciiCircRejAdjs climb on both sides as each rejects the other's Hello, even though the underlying physical link and encapsulation are perfectly healthy.