A tuft or lock of hair on the crown of the head, a crest, topknot, plume.
From the time of the Vedas, the shikha was a distinguishing feature of the Brahmins, Kshatriyas and Vaishyas.
It signified the "twice-born" or all those whose Upanayanam has been performed. At the time of Chudakarana, a tuft of hair was left on the head, never to be cut. This shikha covered a large part of the brain. According to Sushruta, the reason that a few tufts are left on the head is that at the crown, an artery joins a critical nerve juncture. Since an injury to this part of the head is believed to be fatal, it was considered necessary to protect the area by keeping a tuft of hair over it. The shikha was a symbol of superiority and of cleanliness.
Any religious or auspicious ceremony required the shikha to be tied in a knot.The knot was tied to the accompaniment of the Gayatri Mantra. An untied shikha was a symbol of disgrace, impurity and mourning. During funeral and death ceremonies it was left untied.
Presently the shikha is worn only by Brahmins, especially by practicing priests.
The shikha on the top of the head, represents the shikhara that is raised atop all Hindu temples. Temple architecture is based on the vastu purusha mandala or mystic square, a diagram said to represent the Supreme Being. A temple is considered a symbolic depiction of the Supreme Being, whose head is represented as the shikhara of the temple. And in men, the shikha symbolises the brahamanda on which Brahma is said to reside.