Fixed; determinate; definite; specified; prescribed; settled beforehand: as in the phrase “at a time certain.”Indefinite in the sense of not being specifically named; known but not described: applied to one or more real individual objects or characters, as distinguished from a class of objects or an order of characters; coming under particular observation, but undefined, as to kind, number, quantity, duration, etc.; some particular: as, a lady of a certain age.Some (known but unspecified): followed by of.Established as true or sure; placed beyond doubt; positively ascertained and known; unquestionable; indisputable.Capable of being depended on; trustworthy.Unfailing; unerring; sure; positive: as, a certain remedy for rheumatism.Assured; free from doubt regarding: used absolutely, or with of, and formerly sometimes with on.Sure: with an infinitive: as, he is certain to be there to-morrow.Synonyms Undeniable, unquestionable, undoubted, indubitable, indisputable, incontrovertible, inevitable. Sure, Positive, Certain, Confident, etc. (see confident); unhesitating, undoubting.n. A definite but unstated quantity.n. Certainty.n. In the Roman Catholic Church, prayers said daily at mass for specified persons, as for the members of a guild unable to keep a priest of its own, but who paid so much to a church to have a daily remembrance. Also certainty.Certainly; assuredly.