  While SN impostors resemble the Great Eruption of eta Car in the sense that
their spectra show narrow H lines and they have typical peak absolute
magnitudes of -13 to -14 mag, most extragalactic events observed so far are
quite different from eta Car in duration. Their bright phases typically last
for 100~d or less, rather than persisting for several years. The transient
object UGC2773-OT had a similar peak absolute magnitude to other SN impostors,
but with a gradual 5-yr prediscovery rise. In the 6 yr since discovery, it has
faded very slowly (0.26 mag/yr). Overall, we suggest that its decade-long
eruption is so far the best known analog of eta Car's 19th century eruption. We
discuss extensive spectroscopy of the ongoing eruption. The spectra show
interesting changes in velocity and line shape that we discuss in detail,
including an asymmetric Halpha emission line that we show is consistent with
the ejection of a bipolar nebula that could be very much like the Homunculus of
eta Car. Moreover, changes in the line width, line profile, blue excess
emission resembling that of Type IIn supernovae, and the intensity of Halpha
suggest the presence of strong circumstellar interaction in the eruption at
late times. This supports the hypothesis that the extended plateau of eta Car's
eruption may have been powered by shock interaction as well. One interesting
difference compared to eta Car, however, is that UGC2773-OT so far does not
exhibit the repeated brief spikes in luminosity that have been associated with
binary periastron events.
