The term 'semi hazard' can be defined as a situation that is potentially dangerous, but not necessarily life-threatening. The crossword solution for this term is 'JACKKNIFE, ' which refers to a type of accident that occurs when a vehicle suddenly turns sharply, causing the trailer to swing out and JACKKNIFE. This type of accident is considered a semi hazard because it can cause serious damage to the vehicle and its cargo, but does not usually result in injury or death.