Plain English Meaning
A spin you choose to enter on purpose, rather than one that happens by accident. It is only legal and safe in airplanes the manufacturer has cleared for spinning, flown within the limits set out in that airplane's manual.
Full Definition
Spins deliberately entered by the pilot for training, demonstration, or aerobatic purposes, performed only in airplanes specifically approved for spins and within the conditions, weight, and balance limits stated in the airplane's flight manual or placards.
Context Anchor
Used in spin awareness, spin entry, and spin recovery training, especially when discussing airplane limitations and instructor-supervised .