My feeling is that the terminology isn't always perfectly defined, but you have to use some reasoning on whether the seller is in fact saying what he thinks the cue is or what the main part of cue enthusiasts would say...
For example, I'd say, au contraire to the definitions above, that a merry widow cue, synonymous to a plain jane cue, is a cue with a wrap or a handle of different wood from the forearm of the cue, but without points or inlays.
So I would not call a sneaky pete, which for me is a fullsplice cue without a wrap, a merry widow cue.
In any case, it's like art... in order to understand it you need to read these forums (and why not the blue book), and try to understand what people are in fact saying, by using a certain type of common sense... that of the pool enthusiasts.