Supernova ( SN ) 2016bdu is an unusual transient resembling SN 2009ip .
SN 2009ip-like events are characterized by a long-lasting phase of erratic variability which ends with two luminous outbursts a few weeks apart .
The second outburst is significantly more luminous ( about 3 mag ) than the first .
In the case of SN 2016bdu , the first outburst ( Event A ) reached an absolute magnitude M _ { r } \approx - 15.3 mag , while the second one ( Event B ) occurred over one month later and reached M _ { r } \approx -18 mag .
By inspecting archival data , a faint source at the position of SN 2016bdu is detectable several times in the past few years .
We interpret these detections as signatures of a phase of erratic variability , similar to that experienced by SN 2009ip between 2008 and mid-2012 , and resembling the currently observed variability of the luminous blue variable SN 2000ch in NGC 3432 .
Spectroscopic monitoring of SN 2016bdu during the second peak initially shows features typical of a SN IIn .
One month after the Event B maximum , the spectra develop broad Balmer lines with P Cygni profiles and broad metal features .
At these late phases , the spectra resemble those of a typical Type II SN .
All members of this SN 2009ip-like group are remarkably similar to the Type IIn SN 2005gl .
For this object , the claim of a terminal SN explosion is supported by the disappearance of the progenitor star .
The similarity with SN 2005gl suggests that all members of this family may finally explode as genuine SNe , although the unequivocal detection of nucleosynthesised elements in their nebular spectra is still missing .