  The H.E.S.S. Galactic plane scan has revealed a large population of Galactic
very high energy (VHE; E > 100 GeV) emitters. The majority of the galactic
sources are extended and can typically be associated with pulsar wind nebulae
(35%) and supernova remnants (21%), while some of the sources remain
unidentified (31%). A much smaller fraction of point-like sources (5 in total,
corresponding to 4%) are identified as gamma-ray binaries. Active galactic
nuclei located behind the Galactic plane are also a potential source class. An
active galaxy could be identified in the VHE regime by a point-like appearance,
a high variability amplitude (up to a factor of 100) and a typically soft
spectrum (due to absorption by the extra-galactic background light). Here we
report on VERITAS observations of HESS J1943+213, an unidentified point source
discovered to emit above 470 GeV during the extended H.E.S.S. Galactic plane
scan. This source is thought to be a distant BL Lac object behind the Galactic
plane and, though it exhibits a steep spectrum it is a weak GeV source, only
recently detected using 5 years of Fermi-LAT data. Deep VERITAS observations at
high elevations result in the most significant VHE detection of this object so
far, with an excess above 200 GeV of more than 18 standard deviations. We use
variability and spectral analyses of VERITAS data on HESS J1943+213 in a
multi-wavelength context to address the source classification.
