1. A concretion on the hair; the lesion of piedra: In the condition of tricholith, piedra is either of two diseases resulting from fungal infection of the hair shafts. Black piedra occurs mainly in and on the hairs of the scalp and is caused by piedraia hortae; white piedra occurs in and on the hairs of the scalp, beard, moustache and genital areas and is caused by trichosporon beigelii.

2. A calcified hair ball within the stomach or intestines: A tricholith is a calcified concretion that is like a hard, stone-like object that develops from swallowed hair.