SynonymDefinitionAntonym.com - English Synonym Dictionary

Having or feeling no doubt or uncertainty; confident and assured

Certain to occur; destined or inevitable

Definitely or positively (`sure' is sometimes used informally for `surely')

Exercising or taking care great enough to bring assurance

Reliable in operation or effect

Physically secure or dependable

Certain not to fail

Infallible or unfailing

(of persons) worthy of trust or confidence

Impossible to doubt or dispute