Penultimate isn't the last word in words for things that are next to last. There is a pair of noun synonyms that are used commonly enough to have gained entry into abridged dictionaries: penult and penultima. Although all three can refer to something that's next to last, penult and penultima are usually a bit more specific; they are used most often to identify the next to last syllable of a word. All three derive from paenultima, the feminine of paenultimus, a Latin root from paene ("almost") and ultimus ("last"). You may occasionally hear the word penultimate used as an intensified version of ultimate, as in "a race they've called 'the penultimate challenge.'" This use isn't typically found in edited prose, however, or in dictionaries. One of our editors discusses it in this video.