  Partially-ordered magnets are distinct from both spin liquids and
conventional ordered magnets because order and disorder coexist in the same
magnetic phase. Here, we determine the nature of partial order in the canonical
frustrated pyrochlore antiferromagnet Gd$_2$Ti$_{2}$O$_{7}$. Using
single-crystal neutron-diffraction measurements in applied magnetic field,
magnetic symmetry analysis, inelastic neutron-scattering measurements, and
spin-wave modeling, we show that its low-temperature magnetic structure
involves two propagation vectors (2-$\mathbf{k}$ structure) with suppressed
ordered magnetic moments and enhanced spin-wave fluctuations. Our experimental
results support theoretical predictions of thermal fluctuation-driven order in
Gd$_{2}$Ti$_{2}$O$_{7}$.
