for certain adv. phr. 1. Without doubt; certainly; surely. 
 He couldn't tell for sure from a distance whether it was George or Tom. 
 He didn't know for certain which bus to take. 
 I know for certain that he has a car. 2. slang Certain. 
 "That car is smashed so badly it's no good any more." "That's for sure!" Compare: SURE THING. 
 [TahlilGaran] English Idioms Dictionary ▲