2. The act or state of falling off or declining from excellence or perfection; deterioration; decay; decline. The declination of monarchy. Summer . . . Is not looked on as a time Of declination or decay. (Waller)
6. The arc of the horizon, contained between the vertical plane and the prime vertical circle, if reckoned from the east or west, or between the meridian and the plane, reckoned from the north or south.
7. The act of inflecting a word; declension. See decline, v. T. Angle of declination, the angle made by a descending line, or plane, with a horizontal plane. Circle of declination, a circle parallel to the celestial equator.
(Science: physics) declination compass, a compass arranged for finding the declination of the magnetic needle. Declination of the compass or needle, the horizontal angle which the magnetic needle makes with the true north-and-south line.