Plain English Meaning
When you're flying alone, there is no co-pilot to share the workload, catch your mistakes, or hand you a chart. SRM is the set of habits and skills you use to manage everything yourself — the airplane, the avionics, the weather, your own fatigue, and the decisions you have to make — so the flight stays safe.
Full Definition
Single-pilot resource management is the art and science of managing all available resources — both inside and outside the cockpit — to ensure a safe flight when operating as the sole pilot. It applies the principles of crew resource management to the single-pilot environment, covering aeronautical decision-making, risk management, task management, , , and .