  The dynamical properties of single crystal 1T-TaS$_{2}$ are investigated both
in commensurate charge density wave state (CCDW state) and hidden charge
density wave state (HCDW state). We develop a useful criterion in time-domain
transmission terahertz measurement to judge whether the compound is driven into
a metastable state or still in its virgin state. An increase of terahertz
conductivity by two orders of magnitude from CCDW state to HCDW state is
obtained by taking account of the penetration depth mismatch, which is in
agreement with reported \emph{dc} transport measurement. Upon weak pumping,
only transient processes with rapid decay dynamics are triggered in both CCDW
and HCDW states. We compare the conductivity increases in terahertz frequency
range between transient and HCDW states and suggest that fluctuated metallic
domain walls may develop in the transient states.
