What is the geometry of the central carbon atom of a tert-butyl radical?

Trigonal planar

Trigonal planar is a molecular geometry that results when there are three bonds and no lone pairs around the central atom in the molecule. The pairs are arranged along the central atoms equator with 120 degrees angle between them. Molecules with this geometry have sp2d hybridization at the central atom. The central carbon atom of a tert-butyl radical has this type of geometry.