Put to the proof is an idiom that means to TEST or verify something. It can be used in a variety of contexts, from verifying the accuracy of a statement to testing the strength of a material. The two crossword solutions for this term are TEST (4 letters) and TRIED (5 letters). TEST implies that something is being examined or evaluated, while TRIED suggests that something has been put through a process of trial and error. Both words imply that something is being tested or verified in order to prove its validity.