The Flexitarian Diet is a plant-based or vegetarian style of eating that allows for some animal products in moderation.
“Flex” comes from “flexible” and “tarian” comes from “vegetarian,” so a flexitarian is more or less a “flexible vegetarian.”
In 2012, the term “flexitarian” actually entered the Merriam-Webster Dictionary as “one whose normally meatless diet occasionally includes meat or fish.”
Another way to think of flexitarians would be as “semi-vegetarians.”
This version of semi-vegetarianism was first formulated by dietitian Dawn Jackson Blatner, in her book The Flexitarian Diet.
In Blanter’s word:
“You can think of this diet as a ‘vegetarian-ish’ way of eating since this plan touts the basic principles and benefits of a plant-based diet, along with the inclusion of some animal proteins to a lesser extent.”
The goal of the Flexitarian Diet would be to minimize or reduce the frequency of eating meat, without removing it completely.
This is what separates flexitarians from normal omnivores: the former are actively trying to limit meat consumption.
Flexitarians just don’t want to eliminate meat 100% (for health or personal reasons), so they allow some into their diet.