Certain  —adj. 1 a confident, convinced. B indisputable (it is certain that he is guilty). 2 (often foll. By to + infin.) Sure; destined (it is certain to rain; certain to win). 3 unerring, reliable. 4 that need not be specified or may not be known to the reader or hearer (of a certain age; a certain john smith). 5 some but not much (a certain reluctance). —pron. (as pl.) Some but not all (certain of them knew).  for certain without doubt. [latin certus]