“Push the envelope” means to go beyond accepted limits—often through bold innovation or risk-taking. The phrase comes from aviation, where test pilots would push an aircraft to the edge of its flight envelope which is the range of speed, altitude, and maneuverability considered safe.

The “envelope” here refers to engineering boundaries. Pushing it meant flying under extreme conditions to test what a plane (and pilot) could handle.

The phrase took off in popular culture after Tom Wolfe used it in his 1979 book The Right Stuff, about the fearless test pilots and astronauts who redefined what was possible.