Definitions for "Imum Coeli"
The point of the zodiac where the ecliptic intersects the lower part of the meridian, a vertical plane that passes directly north and south. Generally the same as the cusp of the 4th house. See also House.
(or I.C.) - One of the four major angles of a birth chart; this one falls at the bottom of the chart wheel. It is the start of the Fourth House and is one of the most personal points of the chart.
(IC) The fourth house cusp. The Lower Heaven, or Nadir. The north point of the horoscope.