Psychic refers to that which originates 'from the mind'.
Sorceresses of Rossak
During the Butlerian Jihad, and led by Zufa Cenva, the Soceresses of Rossak developed psychic abilities to literally boil the brains of cymeks and neo-cymeks in their brain canisters. This enheightened ability was usually preceded by intense mental focus by the Sorcerress, and then a gathering of static electricity around the practitioner. The resulting psychic blast would then boil the brains of the half-cyborgs, and unfortunately, any humans within radius of the outburst.
Later, during the time near the end of the Corrino Empire and the Ascension of House Atreides, the Bene Gesserit Sisterhood would use psychic energy during their guilt-casting procedure. Typically, led by a sister who was a type of master at the practice, two or three others as well, would surround the pre-decided, intended victim