Definition of sure

• definitely or positively (`sure is sometimes used informally for `surely); "the results are surely encouraging"; "she certainly is a hard worker"; "its going to be a good day for sure"; "they are coming, for certain"; "they thought he had been killed sure enough"; "hell win sure as shooting"; "they sure smell good"; "sure hell come"
• having or feeling no doubt or uncertainty; confident and assured; "felt certain of success"; "was sure (or certain) she had seen it"; "was very sure in his beliefs"; "sure of her friends"
• exercising or taking care great enough to bring assurance; "be certain to disconnect the iron when you are through"; "be sure to lock the doors"