something that is or is supposed to be a certain success, as a bet or a business venture

He thinks that real estate is a sure thing.

something assured; certainty

It's a sure thing that he'll refuse to cooperate.

surely; for sure; O.K.; roger (often used as an interjection).

noun

all sewn up , belief , cert , certainty , cinch , dead certainty , definiteness , destiny , foregone conclusion , lock * , open and shut case , open-and-shut case , positiveness , rain or shine , safe bet , shoo-in , small risk , sure bet , surefire , surety