Noun
(aviation) A zone of indeterminism over a navigation beacon (such as a VOR), where the direction-finding ability of the receiver outputs a random direction as flying over the beacon results in no direction to the beacon, giving a spinning direction indicator display. Also refers to flying over a magnetic pole, and its effects on a magnetic compass.
(biology) A cone-shaped region originating midway between an organism's two ears, and radiating outwards, where a sound's location is indeterminate.
Source: en.wiktionary.org