antoninianus Share definition Flag The antoninianus was a coin used during the Roman Empire thought to have been valued at 2 denarii. I'd like to hear your opinions about this crude imitation of an antoninianus from the time of Gallienus. antoninianus by Greg Fowler May 22, 2007 0 0 Get merch Get the antoninianus mug. Buy Now — $32.95 See more merch