  We present phase-resolved optical spectroscopy of the eclipsing nova-like
cataclysmic variable EC21178-5417 obtained between 2002 and 2013. The average
spectrum of EC21178-5417 shows broad double-peaked emission lines from HeII
4686 \AA{} (strongest feature) and the Balmer series. The high-excitation
feature, CIII/NIII at 4640-4650 \AA{}, is also present and appears broad in
emission. A number of other lines, mostly HeI, are clearly present in
absorption and/or emission. The average spectrum of EC21178-5417 taken at
different months and years shows variability in spectral features, especially
in the Balmer lines beyond H$\gamma$, from pure line emission, mixed line
absorption and emission to pure absorption lines. Doppler maps of the HeII 4686
\AA{} emission reveal the presence of a highly-inclined asymmetric accretion
disc and a two spiral arm-like structure, whereas that of the Balmer lines
(H$\alpha$ and H$\beta$) reveal a more circular accretion disc. There is no
evidence of a bright spot in the Doppler maps of EC21178-5417 and no emission
from the secondary star is seen in the tomograms of the HeII 4686 \AA{} and
Balmer lines. Generally, the emission in EC21178-5417 is dominated by emission
from the accretion disc. We conclude that EC21178-5417 is a member of the RW
Tri or UX UMa sub-type of nova-like variables based on these results and
because it shows different spectral characteristics at different dates. This
spectral behaviour suggests that EC21178-5417 undergoes distinct variations in
mass transfer rate on the observed time scales of months and years.
