To establish the truth or validity of by presentation of argument or evidence. Law To establish the authenticity of (a will). To determine the quality of by testing; try out. Mathematics To demonstrate the validity of (a hypothesis or proposition). Mathematics To verify (the result of a calculation). Printing To make a sample impression of (type). Archaic To find out or learn (something) through experience. To be shown to be such; turn out: a theory that proved impractical in practice. prove out To turn out well; succeed.