We studied the magnetic and crystal structure of the magnetically unstable compound $\mathrm{Gd}{\mathrm{Mn}}_{2}$ using neutron diffraction and x-ray diffraction at ambient pressure and applied pressure up to $4.4\phantom{\rule{0.3em}{0ex}}\mathrm{GPa}$ (neutron) and $16\phantom{\rule{0.3em}{0ex}}\mathrm{GPa}$ (x ray). At ambient pressure, $\mathrm{Gd}{\mathrm{Mn}}_{2}$ shows a short-range antiferromagnetic order with a ferromagnetic component appearing at low temperature. As pressure increases, the Mn moments transform from an intrinsic to an induced state around $1.5\phantom{\rule{0.3em}{0ex}}\mathrm{GPa}$ and then vanish completely. This transformation yields a suppression of the short-range antiferromagnetic correlations imposed by the topologically frustrated Mn sublattice. We show that in the pressure range $2<\mathrm{P}<4\phantom{\rule{0.3em}{0ex}}\mathrm{GPa}$ spin fluctuations on the Mn sites prevent a complete magnetic order in the Gd sublattice. Finally, above $4\phantom{\rule{0.3em}{0ex}}\mathrm{GPa}$, the system recovers a purely ferromagnetic disorder-free magnetic state. We show that $\mathrm{Gd}{\mathrm{Mn}}_{2}$ exhibit a very intriguing and, in some sense, unique interplay between the $f$ and $d$ magnetisms.