A good vegetarian definition takes a few dips and turns to understand when you first decide to become a vegetarian. There are a few different variations.
Most people think that you have decided not to  eat meat anymore. This is a fallacy. There are different types of groups separated by their food choices and values.

Some vegetarians eat dairy products such as eggs, cheese and milk.

A lacto ovo diet doesn’t include meat, fish, or poultry,but does eat eggs, milk, or cheese.

A lacto vegetarian uses milk and cheese but they don’t eat eggs.

A vegan doesn’t eat any meats,animal products or by-products, or any dairy products.They eat fresh veggies, nuts and grains,fruits and legumes.They do not buy any animal or leather products.

They also don’t consume any white sugar due to animal bones used to make the sugar cane white.

Fruitarians only eat fruit because they are perpetual and self generating and don’t need to be planted to reproduce and be a natural food source.

They consider fruits to be the most natural ; in harmony with nature.

Most vegetarians will eat cooked veggies and legumes.

Another group eats only raw food and juices in their diet.This is because to cook is to lose the natural nutrients in the process. To cook veggies around 100 degrees retains the goodness in foods.
It is important to study the nutritive value of the foods that you consume. Make sure that you are getting enough protein, amino acids,Iron,zinc,calcium, vitamin B-12,and vitamin D.With careful planning these can be added efficiently with tofu,fortified cereals,nuts,grains, soy products,pasta,veggies,rice,and legumes.

Muscle and heart health are of the utmost importance.
Studies have been made and show that a vegetarian diet is far more healthy than one with meat consumption.
People with high cholesterol should take a serious look at a vegetarian diet.
I hope this vegetarian definition has answered some questions you have about eating vegetarian.