Final answer:
Shock loading is the term used to describe a sudden or unplanned loading of a crane that increases stress on rigging and the load.
Step-by-step explanation:
The term used to describe a sudden or unplanned loading of a crane that increases the stress on rigging and the load is shock loading. Shock loading occurs when the load being lifted suddenly increases in weight or changes direction, causing a rapid increase in force on the rigging and load. This can result in equipment failure or accidents if the crane and rigging are not designed to handle the sudden increase in stress.