Not definition, mechanics maybe. Spinning Backfist is a knockout technique it doesn't lack any sort of power, you have to dedicate yourself to it, its no bolo punch in my opinion.
If your doing it right there should be about 4 movements, 3 of these are footwork 2 before the strike and 1 after putting you into unorthodox stance at the end. If your throwing before moving the back leg your feet will be in a line therefore less balance and power, the arm should be whipped out at the last moment.

i know what you mean tom. i dont think a spining back fist is a bolo either.

i think chen zen is talking a bout a simple back fist with out the spining motion.

No, it isn't I'm afraid.

oh well, thats cool.

i would never use a spining back punch anyway.

Why not? It has a high rate of hitting when people circle to your blind spot. Peter Aerth actually knocked someone out using this technique.

Just because you're spinning doesn't mean it's flashy and ineffective.

-Taison out

I wasnt talking about a spinning backfist, and no, it isnt a legal punch in boxing. Some kickboxing maybe, but boxing no.

Me confused...

Chen's talking about the back fist,
Jer_sm's talking about spinning back fist,
Tom's talking about spinning back fist,
Prizewriter is talking about back fist. . .

Are you guys having the same conversation?!?!>!

In boxing, the spinning back fist isn't allowed, in K-1 however it is. Back fist in general isn't favored in the boxing world, if you hit, you hit with the front of your knuckles. But I don't really care what they say, I'll hit with whatever I want to hit with, it's my body.

-Taison out

If your quick enough, your backfist will resemble a jab anyways.

ok ok we got mixed up lol, just so back Taisons argument up a spinning back fist is an amazing technique!! it can be used if your leg ever gets turned, someone shifting to the other side of the ring across the ropes etc... check out when bas hit frank with it for example 2:20 http://www.youtube.com/watch?v=h9bJGQBoFTY