Pork is not considered to be poultry, simply because it is not derived from a bird. An example of poultry would be pheasant or chicken meat.
Although it all comes from the meat of an animal, the important thing to consider is which type of animal it comes from. Poultry is exclusive to bird meat, whereas beef is exclusive to cows and pork is exclusive to pigs.
You will find that there are all different kinds of classifications when it comes to meat and pork is most definitely not considered to be poultry because of the fact that it does not come from any type of bird.