The term 'EARTH DESCRIPTOR' can be solved with the 7-letter word 'BIPOLAR'. This term is used to describe the Earth's shape, which is an oblate spheroid. This means that it is slightly flattened at the poles and bulging at the equator. This shape is caused by the Earth's rotation, which causes centrifugal force to pull the planet outward at the equator. The term 'bipolar' is used to describe this shape, as it has two poles.