A vegetarian is an individual who voluntarily excludes any meat-based foods from their diets (not to be confused with herbivores, whose natural diet consists solely of plant-based foods).
Like meat-eaters, vegetarians alsp feed on death. (TOS: "Wolf in the Fold") Charles Tucker once inquired if Colonel Grat was a vegetarian during a dinner invite in 2152. (ENT: "Detained")
Most Vulcans, including T'Pol and Spock were vegetarians. (ENT: "Broken Bow", "Terra Prime"; TOS: "All Our Yesterdays") The v'tosh ka'tur were one major exception. (ENT: "Fusion")
Some Humans, like Chakotay, also chose the life of a vegetarian. (VOY: "Unity", "Workforce") The inhabitants of Omicron Ceti III were also vegetarians. (TOS: "This Side of Paradise")
Deanna Troi became concerned that the Evora may be vegetarians after they began eating the floral arrangements at their reception in 2375. (Star Trek: Insurrection)
The Trill Tobin Dax was a vegetarian. (DS9: "Afterimage")