Pescatarian (sometimes spelled pescetarian with an e) is a word sometimes used to describe those who abstain from eating all meat and animal flesh with the exception of fish. In other words, a pescatarian maintains a vegetarian diet with the addition of fish and other sea foods such as shrimp, clams, crabs and lobster.
In other words, a pescetarian (noun) is a person who eats fish, but doesn't eat steak, chicken, pork or any other kind of meat - only fish and seafood, and a pescetarian (adjective) diet is a diet that includes fish but not steak, chicken, pork or any other kind of meat.
See also: Is fish vegetarian?
Why Do People Go Pescatarian or Eat a Pescatarian Diet?
Although the word is not commonly used and a pescatarian is not technically a vegetarian, more and more people are adopting this kind of diet, usually for health reasons or as a stepping stone to a fully vegetarian diet. What are the reasons for adopting a pescetarian way of eating? Proponents cite roughly the same motivators as full vegetarians and even vegans: personal health weight-loss and longevity, a reduced environmental footprint, and animal cruelty concerns.
Pescetarians often believe that moderate consumption of fish or fish oils, which are high in Omega-3 fatty acids, is necessary for optimum health, although vegetarian alternatives, such as flax seed oil, are available.
See also: What is a vegan?
So, Is a Pescatarian a Vegetarian??
To be 100% clear, a vegetarian diet excludes all animals; and fish are animals. Therefore, a diet that includes fish, or a person who consumes fish cannot be properly called a vegetarian. A pescatarian is NOT a vegetarian, and a vegetarian diet does not include fish.
Is a Pescatarian the Same as a Semi-vegetarian or a Flexitarian?
Not really, but sort of.
A "semi-vegetarian" or a "flexitarian" is someone who eats a mostly vegetarian diet, occasionally supplemented by meat, though there's no real agreed upon definition of how often one can eat meat and still call themselves a semi-vegetarian or a flexitarian: Once a day? Once a week? Once a month? Pescetarians are not restricted to "occasional" fish and may eat fish as little or as frequently as they prefer.
For more on whether or not a pescetarian is a vegetarian and whether or not vegetarians eat fish (and what the whole debate has to do with four-sided triangles and an omnipotent being), see also: