Microcosmic Orbit
Focus your mind upon the natural movement of the kundalini, which starts in the back tailbone (male principle), moves up the spine, past the neck, stops at the top lip and changes polarity moving down the front of the body (female principle) from the top lip to the tailbone. This circular movement of energy is the “microcosmic orbit”, of which all life force moves in our central column or hara line. By focusing your mind gently in meditation on its natural circular movement, intend to move and clear blockages as you strengthen the inner pathway of the life force flow.
Reference
Term first found in HGS Manual: Page 24