to bring forth stillborn, nonviable, or premature offspring. to become checked in development so as to degenerate or remain rudimentary. to terminate a procedure prematurely. to induce the abortion of or give birth to prematurely. to terminate the pregnancy of before term. to terminate prematurely: CANCEL. to stop in the early stages. the premature termination of a flight (as of an aircraft or spacecraft), a mission, or an action or procedure relating to a flight.