magnetic meridian

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A line passing through both magnetic poles of the earth.

from the GNU version of the Collaborative International Dictionary of English.

• noun (Physics) An imaginary line passing through both magnetic poles of the earth.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun an imaginary line passing through both magnetic poles of the Earth