The Collaborative International Dictionary of English v.0.48:

Penultima \Pe*nul"ti*ma\, n. [L. (sc. syllaba), fr. penultimus,
   paenultimus, the last but one; paene almost + ultimus the
   last.]
   Same as Penult.
   [1913 Webster]

WordNet (r) 3.0 (2006):

penultima
    n 1: the next to last syllable in a word [syn: penult,
         penultima, penultimate]