  We report on broadband X-ray properties of the Rabbit pulsar wind nebula
(PWN) associated with the pulsar PSR J1418-6058 using archival Chandra and
XMM-Newton data, and a new NuSTAR observation. NuSTAR data above 10 keV allowed
us to detect the 110-ms spin period of the pulsar, characterize its hard X-ray
pulse profile, and resolve hard X-ray emission from the PWN after removing
contamination from the pulsar and other overlapping point sources. The extended
PWN was detected up to $\sim$20 keV and is well described by a power-law model
with a photon index $\Gamma\approx$2. The PWN shape does not vary significantly
with energy, and its X-ray spectrum shows no clear evidence of softening away
from the pulsar. We modeled the spatial profile of X-ray spectra and broadband
spectral energy distribution in the radio to TeV band to infer the physical
properties of the PWN. We found that a model with low magnetic field strength
($B\sim 10$ $\mu$G) and efficient diffusion ($D\sim 10^{27}$ cm$^2$ s$^{-1}$)
fits the PWN data well. The extended hard X-ray and TeV emission, associated
respectively with synchrotron radiation and inverse Compton scattering by
relativistic electrons, suggests that particles are accelerated to very high
energies ($\gtrsim500$ TeV), indicating that the Rabbit PWN is a Galactic
PeVatron candidate.
