This is the tendency of people with the benefit of hindsight, to falsely believe they would have predicted the outcome of an event. This affects probability elicitation because once outcomes are observed, the assessor may assume that they are the only outcomes that could have happened and underestimate the uncertainty in the outcomes that could have happened, but didn't. By doing this we are preventing ourselves in future episodes, from learning from the past.
Warning people of the dangers of this bias has little effect. In hindsight we are anchored, and cannot truly reconstruct our foresightful state of mind. It is better to argue against the inevitability of the reported outcome and convince oneself that it might have turned out otherwise.