magnetic dip

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. The angle that a magnetic needle makes with the horizontal plane at any specific location. Magnetic dip is 0° at the magnetic equator and 90° at each of the magnetic poles. Also called magnetic inclination.

Wiktionary

1. n. The angle between magnetic north and the horizontal (as shown by a compass held vertically).

GNU Webster's 1913

1. n. The angle that a magnetic needle makes with the plane of the horizon.

WordNet 3.0

1. n. (physics) the angle that a magnetic needle makes with the plane of the horizon