Source : Webster's Revised Unabridged Dictionary (1913)

Penultimate \Pe*nul"ti*mate\, a.
   Last but one; as, the penultimate syllable, the last syllable
   but one of a word.

Penultimate \Pe*nul"ti*mate\, n.
   The penult.

Source : WordNet®

penultimate
     adj : next to the last; "the author inadvertently reveals the
           murderer in the penultimate chapter"; "the figures in
           the next-to-last column" [syn: {next-to-last}]
     n : the next to last syllable in a word [syn: {penult}, {penultima}]