Hirsutism is defined as the excessive growth of thick, dark hair in women in locations where hair growth is normally minimal or absent. Such male-pattern growth of terminal body hair usually occurs in androgen-sensitive 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 and Indian subcontinents 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 blonde or fair-skinned persons.

Most of the time hirsutism is a benign, genetically determined condition that is a cosmetic nuisance for women, however it is important to evaluate for an underlying endocrinopathy in certain situations.