1. A condition in which the hair adjacent to a natural orifice turns inward and causes irritation; e.g., an inversion of an eyelid (entropion), eyelashes irritate the eye. Synonyms: trichoma, trichomatosis.
2. A disease of the eye, in which the eyelashes, being turned in upon the eyeball, produce constant irritation by the motion of the lids.

The acquired type usually follows an inflammatory condition that produces distortion of sight.

3. Hair growing in toward an orifice or against the eyeball.
4. The presence of minute hairlike filaments in the urine.

An incurvation of the hairs around the anus, consequently irritating the mucous membrane.