Wiktionary
n. 1 Short, fine, light-colored, and barely noticeable hair that develops on most of a person's body from his/her childhood. 2 An individual strand of vellus hair
Wikipedia
Vellus hair is short, thin, light-colored, and barely noticeable thin hair that develops on most of a person's body during childhood. Exceptions include the lips, the back of the ear, the palm of the hand, the sole of the foot, some external genital areas, the navel and scar tissue. The density of hair – the number of hair follicles per area of skin – varies from person to person. Each strand of vellus hair is usually less than 2 mm (1/13 inch) long and the follicle is not connected to a sebaceous gland.
Vellus hair is most easily observed on children and adult women, as they generally have less terminal hair to obscure it. Vellus hair is not lanugo hair. Lanugo hair is a much thicker type of hair that normally grows only on fetuses.
Vellus hair is differentiated from the more visible terminal or androgenic hair, which develops only during and after puberty, usually to a greater extent on men than it does on women.
The Latin language uses the word vellus to designate "a fleece" or "wool". In modern usage, vellus hair is sometimes referred to as "peach fuzz."