The 'half man half woman', and (usually) referring to Shiva and 'Shakti' (the energies are depicted in various forms depending on time, space, circumstances).

Refers to the 'Shiv Shakti' (union of male and female) has many symbolic meanings depending on the context:
1) creation (fire and hearth)
2) procreation (through combining the male 'Linga' (penis) and the female 'Yoni' (vagina).
2) ultimate unity
3) harmony
4) combined strength of male and female virtues (androgenous form)
5) primordial energy/essence

Within Sanatan Hindu Sikh Shastar Vidiya, this represents the highest form of 'Kal Yudhan' (combat that leads to death). Visually depicted as an ancient Hindu icon with a central 'Linga' seated in a half-moon crescent, adopted by the Sikh Gurus and is now known as the 'Khanda'.

Also see 'Chandi', 'Khanda', 'Mahakal', 'Shiva', 'Sat Dev Ang Yudhan'.