We use the term "KO" in a broader sense than we actually should. Personally, I have three categories:
1) Toys that directly imitate the real deal, give or take a few details. Bootlegs, a sub-category of that, take that to the limit, imitating everything possible, down to the packaging.
2) Knock-Offs with changes done when compared to the original toy. That includes:
- up- or downsizing
- new or retooled parts
- colors from the rainbow and then some
Toys that share engineering would also fall under this category, even if the mold is totally original.
3) Non-Transformer based toys. Calling them KO's would be doing them a disservice, but more often than not, they're actually based on more obscure robot toys from Japan. There are some that are actually Japan-only, but KO's of them can be found all over.
You should try and hang out at the
3rd Party & Knock-Offs Forum (do it at your own risk however, especially concerning 3rd Party), especially at the local haul threads there.