It means both heart, mind, and spirit. The moon (getsu) is symbolic of enlightenment, perfection, and other worldliness. Title can be Spirit Perfection or Enlightenment of the Mind.
Known as Pounding Drum Piece the title conveys the incessant strivings involved in spiritual practice. The fast tempo and forceful breathing is said to indicate manifestations of the mind under strict discipline.
The title may be interpreted as overcoming a difficult task in a less than perfect way. This piece is meant to encourage the overcoming of difficulties.