  We discuss a mechanism of microwave absorption in conventional
superconductors which is similar to the Debye absorption mechanism in molecular
gases. The contribution of this mechanism to the \emph{ac} conductivity is
proportional to the inelastic quasiparticle relaxation time
$\tau_\mathrm{\mathrm{in}}$ rather than the elastic one $\tau_{\mathrm{el}}$
and therefore it can be much larger than the conventional one. The Debye
contribution to the linear conductivity arises only in the presence of a
\emph{dc} supercurrent in the system and its magnitude depends strongly on the
orientation of the microwave field relative to the supercurrent. The Debye
contribution to the nonlinear conductivity exists even in the absence of
\emph{dc} supercurrent. Since it is proportional to $\tau_{\mathrm{in}}$ the
nonlinear threshold is anomalously low. Microwave absorption measurements may
provide direct information about $\tau_\mathrm{in}$ in superconductors.
