Cannibalism is defined as humans eating humans or animals eating their own kind. I'm not aware of a word that refers to sentients eating sentients of a different species. The concept does raise some questions that are interesting if unpleasant to think about. If you find orc porc disturbing, is it more because orcs are (kind of) intelligent or more because they resemble humans? Are you equally disturbed by dragon steak? How about in settings where dragons are depicted as purely malevolent?
Food for thought.
I mean, I feel vaguely uncomfortable IRL already eating fairly-intelligent animals like octopus or pork. But that's because I'm systematically causing their deaths, not because I'm eating them, per se.
However, I would probably start by drawing the line at intelligent species capable of coherent communication, unless after talking to them they were okay with being eaten. The main issue with cannibalism, aside from prions and whatnot, is primarily how it engenders bad feelings among those who survived, or alternatively, respect for the wishes of the dead. I don't really care what anyone/anything's physical shape is in all that.
It is probably worth briefly stepping aside for a moment when discussing this to note that both the concept and the implicit
ranking of corpse desecration we have is highly anthropocentric—we usually think cannibalism (or, for instance, necrophilia) is significantly more "horrid" than, say, sticking someone's head on a pike on a wall, medieval-style, to rot. There's probably a bunch of animals even on our own earth who would think us perfectly crazy for this assessment if we could explain it to them. Plenty of thoughtful people have come up with fantasy races who would think it
disrespectful to not eat a perfectly good corpse, and that rings true too.
My discomfort with the "eating orcs" trope in particular however is—granted an assumed culture where 'cannibalism'
is verboten for cultural reasons not grounded solely in disease when it's among the 'good races'—how it fits into the pattern of dehumanization of "those ugly, brutal races that are basically animals" (even when, as here, we see they definitely are people!). It gives off very bad vibes. Both of the "unexamined fantasy racism" type and the "we shall consider invalid the personhood of anyone we are at war with" variety. (And, in that meta-context I suppose I
do care a bit that they're humanoid, because it makes the parallels to IRL racism/vendettas all the more uncomfortable.)