Definitions of Risk
Ask three different risk practitioners the definition of risk, and you’ll get at least five different answers. Some of the more common definitions are listed below:

“An uncertain event or condition that, if it occurs, has a positive or negative effect on a project’s objectives.”
PMI® PMBOK® Guide Third Edition

“Risk is the possibility of suffering loss.”
Software Engineering Institute

“The combination of 1) the probability (qualitative or quantitative) that a program or project will experience an undesired event such as cost overrun, schedule slippage, safety mishap, or failure to achieve a needed technological breakthrough; and 2) the consequences, impact, or severity of the undesired event were it to occur.”
NASA 7120.5A Program and Project Management