Someone who, for any of several possible reasons, does not eat warm-blooded animals or land animals. For instance, such a person may dislike the enslavement and cruelty inflicted on animals in factory farms; or one may be repulsed by the idea of eating another mammal. In other cases, one may simply practice pescovegetarianism for health reasons rather than ethical ones. Due to the apparently contradictory nature of the term, it is extremely liable to provoke glib knee-jerk reactions in others.
person #1: You eat fish? What a hypocrite you are, fish aren't vegetables. They suffer too.
person #2: You ass, you didn't even ask me why I'm a pescovegetarian.
person #3: No kidding. What a contemptible non sequitur person #1 just made. The day someone coins a less clumsy word to denote a person whose meat diet is limited to cold-blooded sea animals, is the day I'll drop the term pescovegetarianism in exchange for that other, more descriptive, yet-to-be-coined term.