The risk factor was the inherent level of risk involved in an action.
In 2269, Kaz noted that his plan for the USS Enterprise to disintegrate after the dual Enterprise-IKS Klothos ship left the Delta Triangle had a high risk factor, given how long it would take to execute and Captain James T. Kirk's naturally suspicious mind. (TAS: "The Time Trap")
In 2366, when Captain Jean-Luc Picard queried whether Geordi La Forge had analyzed the risk factor in a proposed maneuver, the chief engineer claimed their chances of success or failure were even money. (TNG: "Booby Trap")