From BiblePortal Wikipedia

Webster's Dictionary [1]

(1): ( v. t.) To fortify or inclose with a mound.

(2): ( n.) An artificial hill or elevation of earth; a raised bank; an embarkment thrown up for defense; a bulwark; a rampart; also, a natural elevation appearing as if thrown up artificially; a regular and isolated hill, hillock, or knoll.

(3): ( n.) A ball or globe forming part of the regalia of an emperor or other sovereign. It is encircled with bands, enriched with precious stones, and surmounted with a cross; - called also globe.

Cyclopedia of Biblical, Theological and Ecclesiastical Literature [2]

(Lat. mundus) is a term in heraldry, designating a globe surmounted with a cross (generally) pattee. As a device, it is said to have been used by the emperor Justinian, and to have been intended to represent the ascendency of Christianity over the world. The royal crown of England is surmounted by a mound, which first appears on the seal of William the Conqueror, though the globe without the cross was used earlier.