SpinorVBarD[p, m] denotes a \bar{v}(p,m)-spinor that depends on the D-dimensional momentum p.
Overview, Spinor, SpinorUBar, SpinorU, SpinorV, SpinorVBar, SpinorUBarD, SpinorUD, SpinorVD.
SpinorVBarD[p, m]\bar{v}(p,m)
SpinorVBarD[p, m] // FCI // StandardForm
(*Spinor[-Momentum[p, D], m, 1]*)SpinorVBarD[p]\bar{v}(p)
SpinorVBarD[p] // FCI // StandardForm
(*Spinor[-Momentum[p, D], 0, 1]*)SpinorVBarD[p] . GSD[p]
DiracEquation[%]\bar{v}(p).(\gamma \cdot p)
0