A carbanion is a negatively charged, trivalent carbon ion that acts as a reactive intermediate in many organic reactions.
With three bonds and 8 electrons, carbanions are electron rich and act as a base forming a C-H bond or as a nucleophile forming a C-C bond.
An alkyl carbanion is sp3 hybridized and has a distorted tetrahedral (trigonal pyramidal) shape with the excess two electrons (lone pair) occupying one of the vertices.
The lone pair exerts repulsion on the electrons of the bond pair lowering the bond angle to less than 109.5o, the tetrahedral bond angle.
The alkenyl/aryl and alkynyl carbanions have bent and linear geometries.