There are many synonyms for the phrase "prove out" which mean to demonstrate or establish the truth or validity of something. Synonyms include to verify, confirm, validate, substantiate, authenticate, corroborate, attest, demonstrate, exhibit, manifest, evince, ascertain, certify, and prove. Each of these words brings a slightly different connotation to the idea of proving something, but they all communicate the same essential meaning. Whether you are verifying the results of an experiment, substantiating a claim, or demonstrating the effectiveness of a product, these synonyms for "prove out" can help you communicate your message clearly and effectively.