A far-IR reflectance spectrum of a disordered Ba(Zn1/3Ta2/3)O-3 dielectric resonator has been studied. The spectrum was analyzed with the Generalized Oscillator model. The real part of the dielectric constant (epsilon (r)) and loss tangent (tan delta) calculated from the parameters obtained from the fit is comparable to the values measured at microwave frequencies. The possible mode identification and their individual mode contribution to the real and imaginary parts of the complex dielectric constant are also analyzed.