  We experimentally identify coherent spin pumping in the magnon-magnon hybrid
modes of permalloy/yttrium iron garnet (Py/YIG) bilayers. Using broadband
ferromagnetic resonance, an "avoided crossing" is observed between the uniform
mode of Py and the spin wave mode of YIG due to the fieldlike interfacial
exchange coupling. We also identify additional linewidth suppression and
enhancement for the in-phase and out-of-phase hybrid modes, respectively,
\textcolor{black}{which can be interpreted as concerted dampinglike torque from
spin pumping}. Our analysis predicts inverse proportionality of both fieldlike
and dampinglike torques to the square root of the Py thickness, which
quantitatively agrees with experiments.
