The Collaborative International Dictionary
magnetic declination \magnetic declination\ n. The angle (at a particular location) between magnetic north and true north; called also magnetic variation.
magnetic variation \magnetic variation\ n. Same as magnetic declination.
Wiktionary
n. 1 (context military nautical navigation English) In navigation, at a given place and time, the horizontal angle between the true north and magnetic north measured east or west according to whether magnetic north lies east or west of true north. 2 (context cartography English) In cartography, the annual change in direction of the horizontal component of the Earth’s magnetic field.
WordNet
n. the angle (at a particular location) between magnetic north and true north [syn: magnetic declination, variation]
Usage examples of "magnetic variation".
He rechecks the bearing at the compass rose at the bottom and then adjusts by twenty degrees for the local magnetic variation.
It was he who steered by the direction indicator, allowing for magnetic variation and a crosswind, and I with small triumphs who checked our passage over the roads and rivers two thousand feet below and pointed them out to him, earning grins and nods.