adverb definitely or positively (`sure' is sometimes used informally for `surely').
— synonyms: surely, certainly, for_sure, for_certain, sure_enough, sure_as_shooting
adjective having or feeling no doubt or uncertainty.
— synonyms: certain(p)
adjective exercising or taking care great enough to bring assurance.
— synonyms: certain
adjective certain to occur.
— synonyms: certain
adjective physically secure or dependable.
adjective reliable in operation or effect.
— synonyms: certain
adjective (of persons) worthy of trust or confidence.
— synonyms: trusted
adjective infallible or unfailing.
adjective certain not to fail.
adjective impossible to doubt or dispute.
— synonyms: indisputable
Examples
“This investment is a sure thing. The bailiff had a sure grip on the prisoner's arm.”
“He was sure she was lying. I am sure of my eventual death. John was acting sure of himself but in truth had doubts.”