outer core

Short definition from Wiktionary

Noun

1. 1
   The hot liquid material found near the centre of some planets, distinct from the solid inner core.
2. 2
   The hot liquid material found near the centre of some planets, distinct from the solid inner core: The part of the Earth between the mantle and inner core, responsible for generating the planet's magnetic field.
3. 3
   Used other than figuratively or idiomatically: see outer, core.