  Multi-wavelength observations of the black hole X-ray binary XTE J1118+480
have offered abundant spectral and timing information about the source, and
have thus provided serious challenges to theoretical models. We propose a
coupled accretion-jet model to interpret the observations. We model the
accretion flow as an outer standard thin accretion disk truncated at a
transition radius by an inner hot accretion flow. The accretion flow accounts
for the observed UV and X-ray emission, but it substantially under-predicts the
radio and infrared fluxes, even after we allow for nonthermal electrons in the
hot flow. We attribute the latter components to a jet. We model the jet
emission by means of the internal shock scenario which is widely employed for
gamma-ray bursts. In our accretion-jet model of XTE J1118+480, the jet
dominates the radio and infrared emission, the thin disk dominates the UV
emission, and the hot flow produces most of the X-ray emission. The optical
emission has contributions from all three components: jet, thin disk, and hot
flow. The model qualitatively accounts for timing features, such as the
intriguing positive and negative time lags between the optical and X-ray
emission, and the wavelength-dependent variability amplitude.
