Guy:
A few times I have commented that a certain story would stand nicely by itself even if it didn't happen to contain a spanking. Believe me, that was a compliment, not a gripe! So surely spanking doesn't always have to be a central theme of a spanking story. In fact, we have hundreds of "spanking" stories here in the LSF that don't even contain a single spanking!
Well, I'd venture that a spanking doesn't have to actually be described within a given account for it to be considered a "spanking story," but from my perspective the spanking (whether actually occurring within the story or not) should be a key plot element in it. I've read, and even infrequently written, stories which involve spanking to some degree, yet wouldn't be classified as "spanking stories" by this standard.
Of course, this Library has a broader, more inclusive (plus arguably less subjective) interpretation of "spanking fiction," which works fine by me for its purposes.
I'd define spanking quite broadly as corporal punishment of the human buttocks via striking them repeatedly, whether by hand (palm), rigid implements (paddles, brushes, wooden spoons, rulers, etc.) and/or flexible or semiflexible ones (canes, switches, straps, belts, whips, crops, sandals, slippers, etc.), in any position that leaves them vulnerable to such correction.
Of and by themselves, I don't consider other forms of physical discipline (bondage, imprisonment, striking other parts of the body, cornertime, tickling, pinching, electrification, forced nudity, sexual teasing, etc.) to be spanking, although of course they could be included in a "spanking story," as long as it involved spanking as a key plot element. (Thighs are a separate body part from buttocks, from my point of view.)
What constitutes a literary work classified as featuring "No Spanking" by Library standards, however, that's an issue that sometimes leaves me baffled...

--C.K.