Navakanya

Skt., nava, "nine"
Skt., kanya, "unmarried"
Nine types of free women

Although the Sanskrit term kanya usually simply designates "a woman not married", the concept of Navakanya is used by several Tantra's to indicate "free" women suited and/or allowed to engage in ritual sexuality.

On reading Tantric scripture it becomes clear that the term kanya, in this context, does not even require the women to be unmarried. Several Tantra's state explicitly that mithunam (Skt. coupling) can be done with one's own wife or husband or with the partner of someone else.

Though most texts merely lay out rules for men, with whom they may or may not do it, we see that by implication also married women were free to engage in extra-marital sexual activity, be it in a sacramental setting. This is revolutionary for the socio-religious structure of Indian society; where orthodox Brahmanic law would punish a woman heavily for doing so.
Different Tantric texts name the following women as being Navakanya:

actress
barber woman
brahmana woman
cowherd woman
kapalika woman
shudra woman
veshya (prostitute)
washer-woman
woman of the garland-maker class

Gupta-Sadhana Tantra

Kumari Tantra

Yoni Tantra

In order to appreciate this list, one must consider that Indian society usually prohibited all women, and all members of the low castes from taking part in important religious rituals. This list then, with the high-caste Brahmana women included with the low-caste Shudra, the actress and prostitute, shows the radical social position that was taken by Tantra; one which made many people come into its fold.

Some texts use the term kulangana instead of navakanja.