  The realization of spin-glass (S-G) state in Heusler alloys is very rare
despite the presence of inherent structural and elemental disorder in those
compounds. Although a few half and full Heusler alloys are known to exhibit S-G
state, there is hardly any manifestation of the same in cases of quaternary
Heusler compounds. Here we report the observation of S-G state in a highly
disordered equiatomic quaternary Heusler compound: FeRuMnGa, where the S-G
state is in between of canonical S-G and cluster glass. Different intricate
features of S-G state including non-equilibrium magnetic dynamics at low
temperature in the compound are unveiled through our comprehensive magnetic,
heat capacity and neutron diffraction studies. The structural disorder in the
sample is neither conventional \textit{A2}- nor \textit{B2}-type while those
two types are commonly observed for Heusler compounds. The presence of disorder
also plays a significant role in electron transport properties of the alloy,
which is reflected in its exhibition of semi-metallic behavior and anomalous
Hall effect at low temperature.
