lacto-vegetarian noun [C]. › a ​person who does not ​eat ​meat, ​fish, or ​eggs but does ​drink ​milk and ​eat some ​foods made from ​milk: As a lacto-vegetarian he ​eats ​cheese, as ​long as it does not ​contain ​animal ​products such as ​rennet. Compare. ovo-vegetarian.