The penultimate thing in a series of things is the last but one.
例句
...on the penultimate day of the Asian Games.在亚运会结束的倒数第二天...in the penultimate chapter.在倒数第二章中
英汉词典释义
adj.
倒数第二的
Y is the penultimate letter of the alphabet.Y是字母表中倒数第二个字母。Italian words usually have the main stress on the penultimate syllable in the word.意大利语单词的主重音通常在倒数第二个音节上。
英英词典释义
Noun
1. the next to last syllable in a word
Adjective
1. next to the last;
"the author inadvertently reveals the murderer in the penultimate chapter""the figures in the next-to-last column"