Is Uluru the biggest rock in the world?

No, Uluru is NOT as rock. A rock sits on the surface unattached. Uluru comprises a formation that continues underground, while now tilted vertically this formation was, (when being made), an alluvial fan.

No. Although commonly believed to be the largest rock in the world, Uluru is second to Mt Augustus (Burringurrah, as it is known by Wajarri Yamatji traditional owners), in Western Australia. Mt Augustus is more than twice the size of Ayers Rock. It rises 717 metres above the stony desert, and extends for a length of 8km - almost the entire circumference of Uluru.