A thoughtform is a manifestation of mental energy, also known as a tulpa in Tibetan mysticism. Its concept is related to the Western philosophy and practice of magic.

(Khanna 1979, p. 21) links mantras and yantras to thoughtforms:

Mantras, the Sanskrit syllables inscribed on yantras, are essentially "thought forms" representing divinities or cosmic powers, which exert their influence by means of sound-vibrations.

A number of prima facie unrelated definitions have been suggested:

Thought Forms (1901) is a book by the Theosophists Annie Besant and C.W. Leadbeater that studies the nature and power of thoughts. It states that thoughts have two effects: "a radiating vibration and a floating form". Thought forms are divided into three classes:

The effect of music, emotions, and colors on thought forms is also described in the book. The effect of the music of Mendelssohn (No. 9 of his "Songs without words"), Gounod (Soldiers Chorus from "Faust") and Richard Wagner (Overture to "The Meistersingers") is analyzed. The music of Wagner produced a "marvellous mountain-range" on the thought forms.