At a given point, the angle between magnetic north and true north. (noun)
Examples of word declination
Between sunrise and the declination is the Sunnat-time, and therefore the best.
 The declination is the variation of the needle from the true meridian of a place.
To learn this we must take out Mercury's declination, which is 24° 43 '18 "N., and the sun's, which is 22° 59' 10 "N.
One of the many methods adopted for mounting equatorials is that exhibited -- with the omission of some minor details -- in fig. 9. _a_ is the polar axis, _b_ is the axis (called the declination axis) which bears the telescope.
It has also another variation, called the declination, or dip.
Columbus is, not for the first observance of the existence of the declination, which is given, for example, upon the map of Andrew Bianca, in 1436, but for the remark which he made on the 13th of September,
You'll need to know your current elevation and something called the declination angle.