1. something or someone which is sure to succeed
Professional
Social
it's a safe bet that he will do the job well
A 'bet' is a financial risk so 'a safe bet' is a noun used to talk about something which is very low risk or guaranteed to succeed. A safe bet is a contradiction in terms as a 'bet' always means there is some level of risk involved, this expression is similar in meaning to 'a sure thing'.