Hirsutism is defined as the excessive growth of thick, dark hair in locations where hair growth in women is normally minimal or absent. Such male-pattern growth of terminal body hair usually occurs in androgen-stimulated locations, such as the face, chest, and areolae.

Although the terms hirsutism and hypertrichosis are often used interchangeably, hypertrichosis actually refers to excess hair (terminal or vellus) in areas that are not predominantly androgen dependent. Whether a given patient is hirsute is often difficult to judge because hair growth varies among individual women and across ethnic groups. What is considered hirsutism in one culture may be considered normal in another. For example, women from the Mediterranean region and Indian subcontinent have more facial and body hair than do women from Asia, sub-Saharan Africa, and Northern Europe. Dark-haired, darkly pigmented individuals of either sex tend to be more hirsute than blond or fair-skinned persons. In women, hirsutism exceeding culturally normal levels can be as distressing an emotional problem as the loss of scalp hair.