antepenultimate
adjective
°Two before the last, i.e., the one immediately before the penultimate, in a series.
"This book has ten chapters — chapter 8 is the antepenultimate one."
noun
°Two before the last in a series. e.g. (..., antepenultimate, penultimate, ultimate).
°The syllable that comes two before the last in a word.