> 2) Webster's defines "oblique (case)" as "a grammatical case other
> than the nominative and vocative".
Umm. Linguist writers tend to be oblique about oblique cases, to the
point you sometimes think they are talking about a specific
grammatical case. In my experience, they seem to be speaking of the
accusative, and seemingly, never of the dative, but my own knowledge
collapses at this point, so I'm only giving an impression.