Definitions for ozone hole
Random House Webster's College Dictionary
any part of the ozone layer that has become depleted by atmospheric pollution, resulting in excess ultraviolet radiation passing through the atmosphere.
Origin of ozone hole:
an area of the ozone layer (near the poles) that is seasonally depleted of ozone
A region of the stratosphere over Antarctica (and a smaller one over the Arctic) that is depleted of ozone in the local spring.