What is the definition of risk?

a situation involving exposure to danger. 

expose (someone or something valued) to danger, harm, or loss. 

It is an uncertain event or condition that, if it occurs, has a positive or negative effect on the projects objectives. ( PmBok guide definition )

In terms of banking, a risk is an event that may or may not occur in the future and if it does, it may expose the individual or entity to financial, reputational or regulatory loss among others, or a combination of these losses.

"The effect of uncertainty on objectives " ISO31000

risk is the effect of uncertainty on objectives

Note that

An effect is a deviation from the expected — positive and/or negative

Objectives can have different aspects (such as financial, health and safety, and environmental goals) and can apply at different levels such as strategic, organization-wide, project, product and process

Ref. ISO

Risk = Severity x Likelihood

Risk in occupational health and safety could be defined as the likelihood of a substance, material or process to cause harm and its resulting severity.

Risk in banking parlance is any losses that might occur due to non repayment of loans by a customer ( credit risk), decrease in value of bank assets due to fluctuations in market forces like interest rate, exchange rate etc. ( market risk) and losses that may occur to the bank due to poor performance of system or its staff (operational risk)

Anything breakdown which stops the operation.

Risk can be defined as an event could happen in un specific time you don’t know about it,  it could happen after a year , a month , today or as this moment.