Definition 1 of 2
Plain English Meaning
An aircraft that has the right instruments and approvals to be flown in cloud or other low-visibility conditions, using only its cockpit instruments to navigate and stay upright.
Full Definition
An aircraft equipped, certified, and approved to be flown solely by reference to instruments under Instrument Flight Rules (IFR), in conditions where outside visual references may not be available. The aircraft must carry the required instruments, navigation equipment, and certifications, and the pilot must hold a current instrument rating to operate it on an .