  We consider a sterile neutrino to be an unparticle, namely an "unsterile"
neutrino, and study its mixing with a canonical active neutrino via a see-saw
mass matrix. There is no unitary transformation that diagonalizes the mixed
propagator and a field redefinition is required. The unsterile-like propagating
mode features a resonance for anomalous dimension between 0 and 1/3, but the
complex pole disappears when the anomalous dimension is larger than 1/3. The
active-like propagating mode is described by a stable pole, but inherits a
non-vanishing spectral density above the unparticle threshold. We also find
that the radiative decay width of the unsterile neutrino into the active
neutrino (and a photon) via charged current loops is suppressed, and this
suppression weakens the bound from the X-ray or soft gamma-ray background when
one considers the unsterile neutrino to be a dark matter candidate.
