Plain English Meaning
A turn that takes two minutes to go all the way around, or one minute to turn 180 degrees. It is the normal, controlled rate of turn pilots use when flying on instruments or maneuvering carefully.
Full Definition
A turn rate of 3 degrees per second, which completes a 360-degree turn in two minutes. Standard rate is the reference turn rate used in instrument flying and is indicated by the turn coordinator or turn-and-slip indicator.
Context Anchor
Seen in discussions of turn performance, instrument flying, and emergency turn decisions after takeoff.
Derivation
Standard means an agreed reference used for comparison. Rate means how much something changes time. Together, standard rate means an agreed amount of turn per second.