Tonsillolith: A tiny stone (calculus) in the tonsils. Such stones are found within little pockets (crypts) in the tonsils. These pockets typically form in chronic recurrent tonsillitis, and they harbor bacteria. Tonsilloliths are foul smelling because they tend to contain high quantities of sulfur compounds. When crushed, they give off a characteristic rotten-egg smell and can cause bad breath. Tonsilloliths may also give a person the sense that something is caught in the back of the throat. Also known as tonsil stone.