Well, one could define the mountain Chimborazo in Equador as the highest in the world, but only if you measure from the core of the earth rather than from the sealevel. Due to higher centrifugal power from the rotation of the earth this mountain would be the highest in the world if measured that way, and it's still growing because of the shifting of continents. Nevertheless I prefer measuring mountains from the sea level. Following that measure I never heard of a mountain higher than the Everest on our planet.