Which term describes weather conditions that require IFR flight?

The term that describes weather conditions requiring IFR flight is Instrument Flight Rules. This designation refers specifically to the regulations under which a pilot operates an aircraft in low visibility and adverse weather conditions. When the weather does not meet the criteria for Visual Flight Rules (VFR), pilots must rely on their instruments rather than visual references to navigate and control the aircraft, making IFR essential for safety and compliance with aviation regulations. IFR encompasses procedures, navigation methods, and communication protocols that are critical for flying in conditions where pilots cannot see the horizon or land features clearly. This is vital for ensuring the safety of flights during times of reduced visibility due to factors like fog, heavy rain, or snowstorms.