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We present X-ray and multi-band optical observations of the afterglow andhost galaxy of GRB 180418A, discovered by ${\it Swift}$/BAT and ${\itFermi}$/GBM. We present a reanalysis of the GBM and BAT data deriving durationsof the prompt emission of $T_{90}\approx$2.56s and $\approx$1.90s,respectively. Modeling the ${\it Fermi}$/GBM catalog of 1405 bursts (2008-2014)in the Hardness-$T_{90}$ plane, we obtain a probability of $\approx$60% thatGRB 180418A is a short-hard burst. From a combination of ${\it Swift}$/XRT and${\it Chandra}$ observations, the X-ray afterglow is detected to $\approx$38.5days after the burst, and exhibits a single power-law decline with $F_{\rm X}\propto t^{-0.98}$. Late-time Gemini observations reveal a faintr$\approx$25.69 mag host galaxy at an angular offset of $\approx$0.16''. At thelikely redshift range of z$\approx$1-2.25, we find that the X-ray afterglowluminosity of GRB 180418A is intermediate between short and long GRBs at allepochs during which there is contemporaneous data, and that GRB 180418A liescloser to the $E_{\gamma,{\rm peak}}-E_{\gamma,{\rm iso}}$ correlation forshort GRBs. Modeling the multi-wavelength afterglow with the standardsynchrotron model, we derive the burst explosion properties and find a jetopening angle of $\theta_{\rm j} \gtrsim 9-14^{\circ}$. If GRB 180418A is ashort GRB that originated from a neutron star merger, it has one of thebrightest and longest-lived afterglows along with an extremely faint hostgalaxy. If instead the event is a long GRB that originated from a massive starcollapse, it has among the lowest luminosity afterglows, and lies in a peculiarspace in terms of the Hardness-$T_{90}$ and $E_{\gamma,{\rmpeak}}-E_{\gamma,{\rm iso}}$ planes.

GRB 180418A: A possibly-short GRB with a wide-angle outflow in a faint host galaxy