Definition - What does Vikalpa mean?
Vikalpa is a Sanskrit term referring to one of the five types of thoughts, or activities and motions, within the mind. These are called vritti in Sanskrit and the great sage, Patanjali, references them in his definition of yoga: yoga citta vritti nirodha ("yoga is the silencing of the disturbances of the mind").
Vikalpa is imagination, fantasy or illusion. It can mean thinking of situations from the past and imagining different results, daydreaming, thinking of things that do not exist or imagining future situations and events. It is an idea that does not exist in reality.
Yogapedia explains Vikalpa
Classical yoga and the original yogic texts suggest letting all vrittis, including the vikalpa, go. Yogis are advised not to fall for fantasies and the trappings of one's imagination. Instead, one should try to dissolve these ideas, recognizing their emptiness through yoga and meditation.
Although controlled imagination and visualization may be beneficial for yoga practice and daily life, vikalpa is uncontrolled and random, the kind of disturbance of the mind that should be avoided. There is also a term for useful, controlled imagination - kalpana - and this is used for visualization and opening the mind and body, as well as for the removal of obstacles and perceived limitations.