This is something I have been working with and I also needed this definition. The specification is anything that can be touched by an unauthorized person, like an operator or utility person, must meet finger safe specifications. This means that any terminal must be 12mm or less to prevent unintended access by fingers. Any terminals inside a properly interlocked electrical cabinet accessible by only authorized personnel must only meet fist safe specs for safety. This means that if an authorized person were in the interlocked electrical cabinet and they fell accidentally into the cabinet they would not be able to come into contact with any voltage over 50 VAC. Hope this helps.
