A mudra is a posture, gesture or touch which has an effect upon our state of mind. Since body and mind are a unity, the attitude of the mind and the attitude of the body reflect each other.
Brazier defines mudra as a somatic-psychic interface, grounding it in the non-dualism of body-mind as the foundational principle for both Buddhist and therapeutic practice.
, Zen Therapy: Transcending the Sorrows of the Human Mind, 1995thesis