last but one

Adjective

 * 1)  Penultimate, next to last, immediately preceding the end of a sequence, list, etc.

Usage notes
In addition to the Latinate, the traditional English expressions for this idea were last but one and (less often). Following the 1920s, American use has favored to the point that last but one now functions as a Britishism. While last but one continues to be somewhat more popular in Britain, next to last,, etc. have been gaining in popularity.

Synonyms

 * see penultimate