Prove  v. (-ving; past part. Proved or proven) 1 (often foll. By that) demonstrate the truth of by evidence or argument. 2 a (usu. Foll. By to + infin.) Be found (it proved to be untrue). B emerge as (will prove the winner). 3 test the accuracy of (a calculation). 4  establish the validity of (a will). 5  (of dough) rise in bread-making.  not proven (in scottish law) verdict that there is insufficient evidence to establish guilt or innocence. Prove oneself show one's abilities, courage, etc.  provable adj. [latin probo test, approve]