The term, siddha, can be applied to anyone who has mastered sadhana, or spiritual practice that transcends the ego.
In addition to its common use, the siddha may also refer to someone who has reached a high degree of meditative power and physical perfection. This perfection is said to be manifested in a number of ways, including physical immortality and the special ability to fly.
According to Hindu philosophy, a siddha guru can initiate new disciples into yoga practices. Having the aspiration to become a siddha and understanding the discipline required to do so is important for yogis who want to take their spiritual journey to its natural conclusion and complete their transformation into an enlightened soul.