It is normally called "The River" So called because it comes from "The River of Dreams" Quote, and believe me it can be a nightmare, I was involved in a hand with the Ace of diamonds in my hand and by the Turn I had the Nut flush, facing a bet from my opponent I shove all-in and they called, when He turned 2 pair, I felt sure I had him beat, only for him to spike a Full house on the River.
It is never over until that River card is dealt and I have lost count of how many times I have been crushed by that last card. But it also happens when I am in the opposite position holding a Draw and catching it on the River to beat 3 of a kind. So as they say "What comes around, goes around" So I cannot complain.