No, it's really not. Neither NVIDIA nor AMD use it in their own marketing, nor does Intel for its Graphics parts. The tech press does, but (and this is important) only as a means to explanation via reference to the term from the CPU world. And even when they do, they have to throw in a ton of caveats about how "cores" don't match up between the very different architectures, etc...
Apple's use of the term "Quad-Core" in that slide is confusing. I don't see that there's any meaningful doubt about that. The more interesting thing is whether it was deliberately confusing.
"Core" isn't even really that well defined for CPUs, look at the controversy over whether AMD's new architecture is 4 clusters with 8 cores, or if you should really count the the clusters as cores but with two threads each.
A good way to do it might be to count the number of structures that can independently schedule memory operations, in which case AMD is correct to call their chips 8 core, but if you use that definition then the "512 core" GPUs are suddenly only 32 cores. Or you could count independent execution units so that the GPU is still 512 cores, but then your "4 core" CPU is now suddenly 12 cores.
> Neither NVIDIA nor AMD use it in their own marketing, nor does Intel for its Graphics parts.
Imagination Technology (the makers of the SGX 543MPWhatever), though, _does_. A particularly confusing usage; in this context it means 16 SIMDs. NVidia occasionally also refers to the Tegra 3's GPU as being 12 core; _they_ mean that it has 12 SIMD units.
http://www.google.com/search?client=safari&rls=en&q=...