[sure.ly] adv (14c) 1: in a sure manner: a archaic: without danger or risk of injury or loss: safely b (1): with assurance: confidently "answered quickly and ~" (2): without doubt: certainly "they will ~ be heard from in the future --R. J. Lifton"
2: indeed, really--often used as an intensive "you ~ don't believe that" usage see
[2]sure