IPA: /ˌæntɪˈpɛnʌlt/
KK: /ˈæntɪpɪnʌlt/
The third syllable from the end of a word.
In the word 'unhappiness', the antepenult is 'hap'.
Antepenult → It is formed from "ante-" (meaning before) and "paenultima" (from Latin, meaning almost last). The word refers to the syllable that is before the last syllable in a word.
Think of 'ante-' meaning 'before' and 'paenultima' meaning 'almost last' — this helps you remember that the antepenult is the syllable before the last one.