merriam-webster just added the word “pescatarian” in their collegiate dictionary:

according to one of merriam-webster’s editor, a word wins only its place in the dictionary after passing their “carefully edited prose” test.  he added that “if a word appears frequently in print without parentheses, without appearing in italics, without any kind of explanation, then that’s a word that editors and writers assume their readers know and understand, that word should be in the dictionary”.