Antepenúltima
Antepenúltima is a Spanish feminine adjective meaning "third to last" or "penultimate but one." It describes the position of an item that is immediately before the second to last item in a sequence. For example, in a list of five items, the antepenúltima item would be the third item.
The word is formed by the prefix "ante-" meaning "before" and "penúltima," which itself comes from "pen-"
This term is most commonly used in Spanish-speaking countries to denote a specific position in a series.